libcamera: formats: Add planeSize() helpers to PixelFormatInfo

Add two helpers functions to the PixelFormatInfo class to compute the
byte size of a given plane, taking the frame size, the stride, the
alignment constraints and the vertical subsampling into account.

Use the new functions through the code base to replace manual
implementations.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>

src/libcamera/v4l2_videodevice.cpp

@@ -1337,11 +1337,7 @@ std::unique_ptr<FrameBuffer> V4L2VideoDevice::createBuffer(unsigned int index)
 			planes[i].offset = offset;
 
 			/* \todo Take the V4L2 stride into account */
-			const unsigned int vertSubSample =
-				info.planes[i].verticalSubSampling;
-			planes[i].length =
-				info.stride(format_.size.width, i, 1u) *
-				((format_.size.height + vertSubSample - 1) / vertSubSample);
+			planes[i].length = info.planeSize(format_.size, i);
 			offset += planes[i].length;
 		}
 	}