cifs: add missing mount option to /proc/mounts

We were not displaying the mount option "signloosely" in /proc/mounts
for cifs mounts which some users found confusing recently

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>

fs/cifs/cifsfs.c

@@ -530,6 +530,8 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
 
 	if (tcon->seal)
 		seq_puts(s, ",seal");
+	else if (tcon->ses->server->ignore_signature)
+		seq_puts(s, ",signloosely");
 	if (tcon->nocase)
 		seq_puts(s, ",nocase");
 	if (tcon->local_lease)