Move return statement in ssl_srv_check_client_no_crt_notification

The previous placing of the return statement made it look like there
are configurations for which no return statement is emitted; while
that's not true (if this function is used, at least some version of
TLS must be enabled), it's still clearer to move the failing return
statement to outside of all preprocessor guards.

library/ssl_tls.c

@@ -6398,9 +6398,10 @@ static int ssl_srv_check_client_no_crt_notification( mbedtls_ssl_context *ssl )
         return( 0 );
     }
 
-    return( -1 );
 #endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 || \
           MBEDTLS_SSL_PROTO_TLS1_2 */
+
+    return( -1 );
 }
 #endif /* MBEDTLS_SSL_SRV_C */