drm/bridge: anx7625: Drop of_gpio header

This driver includes the deprecated OF GPIO header <linux/of_gpio.h>
yet fail to use symbols from it, so drop the include.

Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Maíra Canal <mairacanal@riseup.net>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220812205746.609107-2-mairacanal@riseup.net