RDMA/srpt: Fix a use-after-free

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

RDMA/srpt: Fix a use-after-free

Change the LIO port members inside struct srpt_port from regular members
into pointers. Allocate the LIO port data structures from inside
srpt_make_tport() and free these from inside srpt_make_tport(). Keep
struct srpt_device as long as either an RDMA port or a LIO target port is
associated with it. This patch decouples the lifetime of struct srpt_port
(controlled by the RDMA core) and struct srpt_port_id (controlled by LIO).
This patch fixes the following KASAN complaint:

BUG: KASAN: use-after-free in srpt_enable_tpg+0x31/0x70 [ib_srpt]
Read of size 8 at addr ffff888141cc34b8 by task check/5093

Call Trace:
<TASK>
show_stack+0x4e/0x53
dump_stack_lvl+0x51/0x66
print_address_description.constprop.0.cold+0xea/0x41e
print_report.cold+0x90/0x205
kasan_report+0xb9/0xf0
__asan_load8+0x69/0x90
srpt_enable_tpg+0x31/0x70 [ib_srpt]
target_fabric_tpg_base_enable_store+0xe2/0x140 [target_core_mod]
configfs_write_iter+0x18b/0x210
new_sync_write+0x1f2/0x2f0
vfs_write+0x3e3/0x540
ksys_write+0xbb/0x140
__x64_sys_write+0x42/0x50
do_syscall_64+0x34/0x80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
</TASK>