drm/bridge/megachips: Drop GPIO header

This file isn't using any interfaces from <linux/gpio.h> so
just drop the include.
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190708112803.12432-1-linus.walleij@linaro.org

drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c

@@ -19,7 +19,6 @@
  *   Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output
  */
 
-#include <linux/gpio.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/of.h>