net: marvell: prestera: fix handling IPv4 routes with nhid

In the Linux kernel, the following vulnerability has been resolved:

net: marvell: prestera: fix handling IPv4 routes with nhid

Fix handling IPv4 routes referencing a nexthop via its id by replacing
calls to fib_info_nh() with fib_info_nhc().

Trying to add an IPv4 route referencing a nextop via nhid:

$ ip link set up swp5
$ ip a a 10.0.0.1/24 dev swp5
$ ip nexthop add dev swp5 id 20 via 10.0.0.2
$ ip route add 10.0.1.0/24 nhid 20

triggers warnings when trying to handle the route:

[ 528.805763] ------------[ cut here ]------------
[ 528.810437] WARNING: CPU: 3 PID: 53 at include/net/nexthop.h:468 __prestera_fi_is_direct+0x2c/0x68 [prestera]
[ 528.820434] Modules linked in: prestera_pci act_gact act_police sch_ingress cls_u32 cls_flower prestera arm64_delta_tn48m_dn_led(O) arm64_delta_tn48m_dn_cpld(O) [last unloaded: prestera_pci]
[ 528.837485] CPU: 3 PID: 53 Comm: kworker/u8:3 Tainted: G O 6.4.5 #1
[ 528.845178] Hardware name: delta,tn48m-dn (DT)
[ 528.849641] Workqueue: prestera_ordered __prestera_router_fib_event_work [prestera]
[ 528.857352] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 528.864347] pc : __prestera_fi_is_direct+0x2c/0x68 [prestera]
[ 528.870135] lr : prestera_k_arb_fib_evt+0xb20/0xd50 [prestera]
[ 528.876007] sp : ffff80000b20bc90
[ 528.879336] x29: ffff80000b20bc90 x28: 0000000000000000 x27: ffff0001374d3a48
[ 528.886510] x26: ffff000105604000 x25: ffff000134af8a28 x24: ffff0001374d3800
[ 528.893683] x23: ffff000101c89148 x22: ffff000101c89000 x21: ffff000101c89200
[ 528.900855] x20: ffff00013641fda0 x19: ffff800009d01088 x18: 0000000000000059
[ 528.908027] x17: 0000000000000277 x16: 0000000000000000 x15: 0000000000000000
[ 528.915198] x14: 0000000000000003 x13: 00000000000fe400 x12: 0000000000000000
[ 528.922371] x11: 0000000000000002 x10: 0000000000000aa0 x9 : ffff8000013d2020
[ 528.929543] x8 : 0000000000000018 x7 : 000000007b1703f8 x6 : 000000001ca72f86
[ 528.936715] x5 : 0000000033399ea7 x4 : 0000000000000000 x3 : ffff0001374d3acc
[ 528.943886] x2 : 0000000000000000 x1 : ffff00010200de00 x0 : ffff000134ae3f80
[ 528.951058] Call trace:
[ 528.953516] __prestera_fi_is_direct+0x2c/0x68 [prestera]
[ 528.958952] __prestera_router_fib_event_work+0x100/0x158 [prestera]
[ 528.965348] process_one_work+0x208/0x488
[ 528.969387] worker_thread+0x4c/0x430
[ 528.973068] kthread+0x120/0x138
[ 528.976313] ret_from_fork+0x10/0x20
[ 528.979909] ---[ end trace 0000000000000000 ]---
[ 528.984998] ------------[ cut here ]------------
[ 528.989645] WARNING: CPU: 3 PID: 53 at include/net/nexthop.h:468 __prestera_fi_is_direct+0x2c/0x68 [prestera]
[ 528.999628] Modules linked in: prestera_pci act_gact act_police sch_ingress cls_u32 cls_flower prestera arm64_delta_tn48m_dn_led(O) arm64_delta_tn48m_dn_cpld(O) [last unloaded: prestera_pci]
[ 529.016676] CPU: 3 PID: 53 Comm: kworker/u8:3 Tainted: G W O 6.4.5 #1
[ 529.024368] Hardware name: delta,tn48m-dn (DT)
[ 529.028830] Workqueue: prestera_ordered __prestera_router_fib_event_work [prestera]
[ 529.036539] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 529.043533] pc : __prestera_fi_is_direct+0x2c/0x68 [prestera]
[ 529.049318] lr : __prestera_k_arb_fc_apply+0x280/0x2f8 [prestera]
[ 529.055452] sp : ffff80000b20bc60
[ 529.058781] x29: ffff80000b20bc60 x28: 0000000000000000 x27: ffff0001374d3a48
[ 529.065953] x26: ffff000105604000 x25: ffff000134af8a28 x24: ffff0001374d3800
[ 529.073126] x23: ffff000101c89148 x22: ffff000101c89148 x21: ffff00013641fda0
[ 529.080299] x20: ffff000101c89000 x19: ffff000101c89020 x18: 0000000000000059
[ 529.087471] x17: 0000000000000277 x16: 0000000000000000 x15: 0000000000000000
[ 529.094642] x14: 0000000000000003 x13: 00000000000fe400 x12: 0000000000000000
[ 529.101814] x11: 0000000000000002 x10: 0000000000000aa0 x9 : ffff8000013cee80
[ 529.108985] x8 : 0000000000000018 x7 : 000000007b1703f8 x6
---truncated---