libcamera: pipeline: ipu3: Cancel unused buffers

When the CIO2 returns a cancelled buffer, we will not queue buffers
to the IMGU.

These buffers should be explicitly marked as cancelled to ensure
the application knows there is no valid metadata or frame data
provided in the buffer.

Provide a cancel() method on the FrameBuffer to allow explicitly
cancelling a buffer.

Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/buffer.h

@@ -53,6 +53,8 @@ public:
 	unsigned int cookie() const { return cookie_; }
 	void setCookie(unsigned int cookie) { cookie_ = cookie; }
 
+	void cancel() { metadata_.status = FrameMetadata::FrameCancelled; }
+
 private:
 	LIBCAMERA_DISABLE_COPY_AND_MOVE(FrameBuffer)