drm/msm: add hdmi support for apq8x74/mdp5

The HDMI block is basically the same between older SoC's with mdp4
display controller, and newer ones with mdp5.

So mostly this consists of better abstracting out the different sets of
regulators, clks, etc.  In particular, for regulators and clks we can
split it up by what is needed for hot plug detect to work, and what is
needed to light up the display.

Also, 8x74 has a new phy.. a very simple one, but split out into a
different mmio space.  And with mdp5, the irq is shared with mdp, so we
don't directly register our own irq handler.

Signed-off-by: Rob Clark <robdclark@gmail.com>