testing: move serial_link_update just after the matrix_scan

should we not process both hand a the same time. moved the
serial_link_update function just below the matrix_scan function so
that when we process the matrix_rows we process both hand of the matrix.

tmk_core/common/keyboard.c

@@ -127,6 +127,11 @@ void keyboard_task(void)
     matrix_row_t matrix_change = 0;
 
     matrix_scan();
+
+#ifdef SERIAL_LINK_ENABLE
+	serial_link_update();
+#endif
+
     for (uint8_t r = 0; r < MATRIX_ROWS; r++) {
         matrix_row = matrix_get_row(r);
         matrix_change = matrix_row ^ matrix_prev[r];
@@ -183,10 +188,6 @@ void keyboard_task(void)
     adb_mouse_task();
 #endif
 
-#ifdef SERIAL_LINK_ENABLE
-	serial_link_update();
-#endif
-
 #ifdef VISUALIZER_ENABLE
     visualizer_update(default_layer_state, layer_state, visualizer_get_mods(), host_keyboard_leds());
 #endif