drm/msm/dpu: Drop unused GPIO code

drm/msm/dpu: Drop unused GPIO code

The DPU has some kind of idea that it wants to be able to
bring up power using GPIO lines. The struct dss_gpio is however
completely unused and should this be done, it should be done
using the GPIO descriptor framework rather than this API
which relies on the global GPIO numberspace. Delete this
code before anyone hurt themselves.

The inclusion of <linux/gpio.h> was abused to get some OF
and IRQ headers implicitly included into the DPU utilities,
make these includes explicit and push them down into the actual
implementation.

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>