drm/imx: handle pending updates better, add plane zpos property support - Add a mechanism to only send commit done events once all pending updates have been applied. This closes a small race window where already armed events could fire even though the double buffered hardware update just missed the update window. - Add plane zpos property support to allow placing the overlay plane behind the primary plane. - Allow building imx-drm on all platforms under COMPILE_TEST. Signed-off-by: Dave Airlie <airlied@redhat.com> From: Philipp Zabel <pza@pengutronix.de> Link: https://patchwork.freedesktop.org/patch/msgid/20190222112350.m3ucezilqx6cyest@pengutronix.de