cifs: make sure we ignore the credentials= and cred= options

Older mount.cifs programs passed this on to the kernel after parsing
the file. Make sure the kernel ignores that option.

Should fix:

    https://bugzilla.kernel.org/show_bug.cgi?id=43195

Cc: Sachin Prabhu <sprabhu@redhat.com>
Reported-by: Ronald <ronald645@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/connect.c

@@ -215,6 +215,8 @@ static const match_table_t cifs_mount_option_tokens = {
 
 	{ Opt_ignore, "cred" },
 	{ Opt_ignore, "credentials" },
+	{ Opt_ignore, "cred=%s" },
+	{ Opt_ignore, "credentials=%s" },
 	{ Opt_ignore, "guest" },
 	{ Opt_ignore, "rw" },
 	{ Opt_ignore, "ro" },