OMAPDSS: HDMI: PHY changes for OMAP5

OMAP5 HDMI PHY has some differences compared to OMAP4 HDMI PHY. This
patch creates a features struct which help the driver configure the PHY
based on what SoC it is.

Some of the features aren't currenlty used, but will come in use later.

Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>