Enable exynos-drm on odroid

The following changes were needed:

1. The new driver needs to talk to the DDC on the remote connected TV,
   to obtain the EDID and detect supported resolutions. This is an i2c device.
   According to Odroid-U2 schematics, this connection is made to I2C2, so we
   set up the I2C2 adapter and bus appropriately.

2. The old driver uses functionality of the samsung HDMI interface to detect
   cable presence. The new driver only accepts GPIO to do this.

3. Board file provides a exynos4-hdmi device, which exynos-drm interprets
   as a HDMI 1.3 device. In that configuration, the pll did not settle, and
   there was no image output. Had to tweak things so that it would get
   recognised as HDMI 1.4.