proc: Fix unbalanced hard link numbers

proc_create_mount_point() forgot to increase the parent's nlink, and
it resulted in unbalanced hard link numbers, e.g. /proc/fs shows one
less than expected.

Fixes: eb6d38d5427b ("proc: Allow creating permanently empty directories...")
Cc: stable@vger.kernel.org
Reported-by: Tristan Ye <tristan.ye@suse.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

fs/proc/generic.c

@@ -472,6 +472,7 @@ struct proc_dir_entry *proc_create_mount_point(const char *name)
 		ent->data = NULL;
 		ent->proc_fops = NULL;
 		ent->proc_iops = NULL;
+		parent->nlink++;
 		if (proc_register(parent, ent) < 0) {
 			kfree(ent);
 			parent->nlink--;