OMAP4: DSS2: HDMI: Function pointer approach to call

HDMI IP fundamentally has replaceable core PHY and PLL blocks.
These blocks might vary across OMAP's but the end functionality such as to
enable or disable PLL, PHY, function to read EDID would remain the same.

Thus to make the current hdmi DSS driver compatible with different OMAP's having
different IP blocks( A combination of different core, PHY, PLL blocks), function
pointer approach is introduced.

With function pointer, relevant IP dependent functions are mapped to the generic
functions used by DSS during the initialization based on the OMAP compiled.
Thus making hdmi DSS driver IP agnostic.

Signed-off-by: Mythri P K <mythripk@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>