imx-drm fixes and color format updates

- Some correctness fixes found by coccinelle
- Add drivers/gpu/ipu-v3 directory to MAINTAINERS
- Add support for more color formats
- Fix a regression, making displays larger than FullHD work again

* tag 'imx-drm-next-2015-10-30' of git://git.pengutronix.de/git/pza/linux:
  drm/imx: hdmi: fix HDMI setup to allow modes larger than FullHD
  gpu: ipu-v3: fix div_ratio type
  gpu: ipu-v3: csi: add support for 8 bpp grayscale sensors.
  drm/imx: enable ARGB4444 16-bit color format
  gpu: ipu-v3: add support for ARGB4444 16-bit color format
  drm/imx: ipuv3-plane: enable support for RGBX8888 and RGBA8888 pixel formats
  gpu: ipu-v3: add support for RGBX8888 and RGBA8888 pixel formats
  drm/imx: enable 15-bit RGB with 1-bit alpha formats
  gpu: ipu-v3: add support for 15-bit RGB with 1-bit alpha formats
  MAINTAINERS: Add IPUv3 core driver to the i.MX DRM driver section
  gpu: ipu-v3: ipu-csi: bool test doesn't need a comparison to false