drm/vmwgfx: Reinstate the legacy display system dirty callback
drm/vmwgfx: Reinstate the legacy display system dirty callback

It somehow got lost in a rewrite.

Signed-off-by: Thomas Hellstrom <a26490dfbee4be3d38287ad6448444504f58193c@vmware.com>
Reviewed-by: Sinclair Yeh <326bbc75ae5821d6c8d1817b260a4d8d0fdf1f63@vmware.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs