gadget: f_thor: annotate switch/case fallthrough

Even though we seem to catch POWEROFF and EFSCLEAR commands in the THOR
protocol request handling, we ultimately do not seem to handle them
(apart from sending a response), so those commands still print an error
message.

Annotate the switch/case fallthrough in this case, to make this clear to
the compiler.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>

drivers/usb/gadget/f_thor.c

@@ -138,6 +138,7 @@ static int process_rqt_cmd(struct udevice *udc, const struct rqt_box *rqt)
 	case RQT_CMD_POWEROFF:
 	case RQT_CMD_EFSCLEAR:
 		send_rsp(udc, rsp);
+		fallthrough;
 	default:
 		printf("Command not supported -> cmd: %d\n", rqt->rqt_data);
 		return -EINVAL;