selinux: remove a useless return

The last return is unreachable, remove the 'return'
in default, let it fall through.

Signed-off-by: WANG Cong <amwang@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

security/selinux/ss/mls.c

@@ -541,8 +541,8 @@ int mls_compute_sid(struct context *scontext,
 	case AVTAB_MEMBER:
 		/* Use the process effective MLS attributes. */
 		return mls_context_cpy_low(newcontext, scontext);
-	default:
-		return -EINVAL;
+
+	/* fall through */
 	}
 	return -EINVAL;
 }