pinctrl: samsung: Add missing header(s)

Do not imply that some of the generic headers may be always included.
Instead, include explicitly what we are direct user of.

While at it, sort headers alphabetically.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

drivers/pinctrl/samsung/pinctrl-samsung.c

@@ -15,15 +15,16 @@
 // but provides extensions to which platform specific implementation of the gpio
 // and wakeup interrupts can be hooked to.
 
-#include <linux/init.h>
-#include <linux/platform_device.h>
-#include <linux/io.h>
-#include <linux/property.h>
-#include <linux/slab.h>
 #include <linux/err.h>
 #include <linux/gpio/driver.h>
+#include <linux/init.h>
+#include <linux/io.h>
 #include <linux/irqdomain.h>
 #include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
 #include <linux/spinlock.h>
 
 #include "../core.h"