drm/bridge: analogix_dp: Convert to GPIO descriptors

This converts the Analogix display port to use GPIO descriptors
instead of DT-extracted numbers.

Cc: Douglas Anderson <dianders@chromium.org>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190609231339.22136-1-linus.walleij@linaro.org