gpio: pcf857x: Sort headers alphabetically

This makes checking for duplicates when adding a new #include easier.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-pcf857x.c

@@ -18,15 +18,15 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
-#include <linux/kernel.h>
-#include <linux/slab.h>
 #include <linux/gpio.h>
 #include <linux/i2c.h>
 #include <linux/i2c/pcf857x.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
+#include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>