fold unix_mknod() into unix_bind_bsd()

mainline inclusion
from mainline-v5.14-rc1
commit 71e6be6f
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4OM1C
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=71e6be6f7d2bada7099d79205779c4452d4fd35b



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

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

Conflicts:
	net/unix/af_unix.c

Signed-off-by: Baisong Zhong <zhongbaisong@huawei.com>
Reviewed-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>