ksmbd: remove unneeded NULL check in for_each_netdev

mainline inclusion
from mainline-5.15-rc1
commit 6cfbcf2f
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I60T7G
CVE: NA

Reference: https://git.kernel.org/torvalds/linux/c/6cfbcf2f40e3



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netdev can never be NULL in for_each_netdev loop.
This patch remove unneeded NULL check.

Reported-by: Coverity Scan <scan-admin@coverity.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>