net/smc: fix a memory leak in smc_sysctl_net_exit()

mainline inclusion
from mainline-v5.18-rc1
commit 5ae6acf1
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I76JHC
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/smc?id=5ae6acf1d00be462d7b08b4a8748798ef595ae5a



--------------------------------

Recently added smc_sysctl_net_exit() forgot to free
the memory allocated from smc_sysctl_net_init()
for non initial network namespace.

Fixes: 462791bb ("net/smc: add sysctl interface for SMC")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Tony Lu <tonylu@linux.alibaba.com>
Cc: Dust Li <dust.li@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Litao Jiao <jiaolitao@sangfor.com.cn>