This syncs the imx-hdmi driver with Linux 4.2-rc1 where it makes sense. This
makes it easier to compare the driver with the kernel. This also adds
hdmi_av_composer which is mandatory. Somehow the driver worked without it in
lower resolutions, but now it also works for higher resolutions.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>