clients/simple-dmabuf-egl: drop Y_INVERT flag
The motivations for this are:
- Y_INVERT is not used by real-world clients. weston-simple-dmabuf-egl is the only known user. Thus this creates a special case just for a demo client.
- Some compositors (wlroots) have dropped support for DMA-BUF flags, so the client no longer runs there.
- Dropping the flag allows compositors to use a KMS hardware plane to display the buffer.
Instead of trying to maintain the previous visual appearance, let's just leave it as-is since it doesn't really matter that the animation bounces between the two opposite corners.
Closes: #675 (closed)
Edited by Simon Ser