drm/msm/hdmi: Convert to use GPIO descriptors

This switches the MSM HDMI code to use GPIO descriptors.
Normally we would fetch the GPIOs from the device with the
flags GPIOD_IN or GPIOD_OUT_[LOW|HIGH] to set up the lines
immediately, but since the code seems eager to actively
drive the lines high/low when turning HDMI on and off, we
just fetch the GPIOs as-is and keep the code explicitly
driving them.

The old code would try legacy bindings (GPIOs without any
"-gpios" suffix) but this has been moved to the gpiolib
as a quirk by the previous patch.

Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <sean@poorly.run>
Cc: linux-arm-msm@vger.kernel.org
Cc: freedreno@lists.freedesktop.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>