ARM: s3c64xx: Use the right include

The file s3c64xx.c is including <linux/gpio.h> despite using no
symbols from the file, however it needs it to implicitly bring in
of_have_populated_dt() so include <linux/of.h> explicitly instead.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

arch/arm/mach-s3c/s3c64xx.c

@@ -21,13 +21,13 @@
 #include <linux/ioport.h>
 #include <linux/serial_core.h>
 #include <linux/serial_s3c.h>
+#include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/reboot.h>
 #include <linux/io.h>
 #include <linux/clk/samsung.h>
 #include <linux/dma-mapping.h>
 #include <linux/irq.h>
-#include <linux/gpio.h>
 #include <linux/irqchip/arm-vic.h>
 #include <clocksource/samsung_pwm.h>