drivers: sensor: mmc56x3_async.c fix missing break

coverity complains of a missing break statement in SENSOR_CHAN_ALL case
this is fixed by adding __attribute__((fallthrough))

Signed-off-by: Jilay Pandya <jilay.pandya@outlook.com>

Author: jilaypandya

drivers/sensor/memsic/mmc56x3/mmc56x3_async.c

@@ -53,9 +53,13 @@ void mmc56x3_submit_sync(struct rtio_iodev_sqe *iodev_sqe)
 		case SENSOR_CHAN_MAGN_Z:
 			edata->has_magn_z = 1;
 			break;
+		case SENSOR_CHAN_MAGN_XYZ:
+			edata->has_magn_x = 1;
+			edata->has_magn_y = 1;
+			edata->has_magn_z = 1;
+			break;
 		case SENSOR_CHAN_ALL:
 			edata->has_temp = 1;
-		case SENSOR_CHAN_MAGN_XYZ:
 			edata->has_magn_x = 1;
 			edata->has_magn_y = 1;
 			edata->has_magn_z = 1;