libcamera: v4l2_device: importBuffers support

Provide the ability to import a BufferPool into the V4L2Device allowing
external dmabuf backed buffers to be queued.

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

src/libcamera/include/v4l2_device.h

@@ -100,6 +100,7 @@ public:
 	int setFormat(V4L2DeviceFormat *format);
 
 	int exportBuffers(BufferPool *pool);
+	int importBuffers(BufferPool *pool);
 	int releaseBuffers();
 
 	int queueBuffer(Buffer *buffer);