libcamera: PixelFormat: Turn into a class

Create a class to represent a pixel format. This is done to add support
for modifiers for the formats. So far no modifiers are added by any
pipeline handler, all plumbing to deal with them is however in place.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/v4l2_videodevice.cpp

@@ -1551,8 +1551,7 @@ uint32_t V4L2VideoDevice::toV4L2Fourcc(PixelFormat pixelFormat, bool multiplanar
 	 * class. Until we fix the logger, work around it.
 	 */
 	libcamera::_log(__FILE__, __LINE__, _LOG_CATEGORY(V4L2)(), LogError).stream()
-		<< "Unsupported V4L2 pixel format "
-		<< utils::hex(pixelFormat);
+		<< "Unsupported V4L2 pixel format " << pixelFormat.toString();
 	return 0;
 }