drm/vc4: Move HDMI reset to pm_resume

Pi0-3 have power domains attached to the pm_runtime hooks
for the HDMI block. Initialisation done in the reset called
from bind is therefore lost if all users of the domain are
suspended.
The VEC shares the same lowest level clock/power gating as
the HDMI block, so whilst that is enabled the block is never
actually powered down, but if it isn't enabled then we lose
the state.

Reset and initialise the HDMI block from pm_resume.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>