libcamera: Use C++17 [[fallthrough]] everywhere

Fixes build failure on some build environments.

Signed-off-by: Matti Lehtimäki <matti.lehtimaki@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/gstreamer/gstlibcamera-utils.cpp

@@ -154,7 +154,7 @@ colorspace_from_colorimetry(const GstVideoColorimetry &colorimetry)
 	case GST_VIDEO_TRANSFER_GAMMA22:
 	case GST_VIDEO_TRANSFER_GAMMA28:
 		GST_WARNING("GAMMA 18, 20, 22, 28 transfer functions not supported");
-	/* fallthrough */
+		[[fallthrough]];
 	case GST_VIDEO_TRANSFER_GAMMA10:
 		colorspace->transferFunction = ColorSpace::TransferFunction::Linear;
 		break;

src/libcamera/camera_sensor.cpp

@@ -427,7 +427,7 @@ int CameraSensor::initProperties()
 			LOG(CameraSensor, Warning)
 				<< "Unsupported camera location "
 				<< v4l2Orientation << ", setting to External";
-			/* Fall-through */
+			[[fallthrough]];
 		case V4L2_CAMERA_ORIENTATION_EXTERNAL:
 			propertyValue = properties::CameraLocationExternal;
 			break;