drm/omap: Fix missing includes

With certain kernel config options many omapdrm files fail to compile
due to missing include of linux/gpio/consumer.h and linux/of.h.

This patch adds those includes.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reported-by: Dan Murphy <dmurphy@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

drivers/gpu/drm/omapdrm/displays/panel-dpi.c

@@ -10,6 +10,7 @@
  */
 
 #include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>