omapfb/dss: Include the right header

The hdmi4.c and hdmi5.c files include the legacy GPIO
header <linux/gpio.h> but does not use any of the symbols
from this file.

What it does use is the implicit inclusion of <linux/of.h>
leading to compile errors if we just drop this include.

Include the right header.

Cc: Tony Lindgren <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>
Signed-off-by: Sam Ravnborg <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/video/fbdev/omap2/omapfb/dss/hdmi4.c

···
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/clk.h>
-#include <linux/gpio.h>
+#include <linux/of.h>
 #include <linux/regulator/consumer.h>
 #include <linux/component.h>
 #include <video/omapfb_dss.h>

drivers/video/fbdev/omap2/omapfb/dss/hdmi5.c

···
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/clk.h>
-#include <linux/gpio.h>
+#include <linux/of.h>
 #include <linux/regulator/consumer.h>
 #include <linux/component.h>
 #include <video/omapfb_dss.h>