drm/msm/hdmi: Use pinctrl in HDMI driver

Some targets (eg: msm8994) use the pinctrl framework to configure
interface pins. This change adds support for initialization and
pinctrl active/sleep state control for the HDMI driver.

Signed-off-by: Stephane Viau <sviau@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>