[Intel-gfx] HDMI 4k support v2

[Damien Lespiau]

Following up the first instance of this series:
  http://lists.freedesktop.org/archives/dri-devel/2013-August/043125.html

Here is a v2 with Ville's review pass and a few additions:
  - Alternate clock modes for 4k resolutions
  - HDMI vendor specific infoframe support in drivers/video/hdmi.c
  - Enabling of those vendor specific infoframes in the i915 driver

Along the way, a tegra patch was needed for a small consolidation of the code
packing vendor specific infoframes. This patch has only been compile-tested.

On Intel, it's possible to read back the programmed infoframe buffers with
intel-gpu-tools' intel_infoframe and this gives:

Vendor InfoFrame:
- frequency: every vsync
- raw:
  f4050181 000c0347 00000320 00000000
  00000000 00000000 00000000 00000000
  0000004c 00000000 00000000 00000000
  00000000 00000000 00000000 00000000
- vendor Id: 0x000c03 (HDMI)
- video format: 0x001 
- HDMI VIC: 3

after a $ xrandr --output HDMI1 --mode 3840x2160 -r 24

-- 
Damien