net: mana: Fix RX buf alloc_size alignment and atomic op panic

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

net: mana: Fix RX buf alloc_size alignment and atomic op panic

The MANA driver's RX buffer alloc_size is passed into napi_build_skb() to
create SKB. skb_shinfo(skb) is located at the end of skb, and its alignment
is affected by the alloc_size passed into napi_build_skb(). The size needs
to be aligned properly for better performance and atomic operations.
Otherwise, on ARM64 CPU, for certain MTU settings like 4000, atomic
operations may panic on the skb_shinfo(skb)->dataref due to alignment fault.

To fix this bug, add proper alignment to the alloc_size calculation.

Sample panic info:
[ 253.298819] Unable to handle kernel paging request at virtual address ffff000129ba5cce
[ 253.300900] Mem abort info:
[ 253.301760] ESR = 0x0000000096000021
[ 253.302825] EC = 0x25: DABT (current EL), IL = 32 bits
[ 253.304268] SET = 0, FnV = 0
[ 253.305172] EA = 0, S1PTW = 0
[ 253.306103] FSC = 0x21: alignment fault
Call trace:
__skb_clone+0xfc/0x198
skb_clone+0x78/0xe0
raw6_local_deliver+0xfc/0x228
ip6_protocol_deliver_rcu+0x80/0x500
ip6_input_finish+0x48/0x80
ip6_input+0x48/0xc0
ip6_sublist_rcv_finish+0x50/0x78
ip6_sublist_rcv+0x1cc/0x2b8
ipv6_list_rcv+0x100/0x150
__netif_receive_skb_list_core+0x180/0x220
netif_receive_skb_list_internal+0x198/0x2a8
__napi_poll+0x138/0x250
net_rx_action+0x148/0x330
handle_softirqs+0x12c/0x3a0