This patch adds support for DMT display modes over HDMI.
The modes timings configurations are from the Amlogic Vendor linux tree
and tested over multiples monitors.
Previously only a selected number of CEA modes were supported.

Only these following modes are supported with these changes:
- 640x480@60Hz
- 800x600@60Hz
- 1024x768@60Hz
- 1152x864@75Hz
- 1280x1024@60Hz
- 1600x1200@60Hz
- 1920x1080@60Hz

The associated code to handle the clock rates is also added.
Acked-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1520935670-14187-1-git-send-email-narmstrong@baylibre.com