mfd: axp20x: Clean up included headers

Add the bitops.h header as we need it, alphabetize header order.
Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>
Signed-off-by: Priit Laes <plaes@plaes.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/mfd/axp20x.c

@@ -16,18 +16,19 @@
  * published by the Free Software Foundation.
  */
 
-#include <linux/err.h>
+#include <linux/acpi.h>
+#include <linux/bitops.h>
 #include <linux/delay.h>
+#include <linux/err.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
+#include <linux/mfd/axp20x.h>
+#include <linux/mfd/core.h>
 #include <linux/module.h>
+#include <linux/of_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
-#include <linux/mfd/axp20x.h>
-#include <linux/mfd/core.h>
-#include <linux/of_device.h>
-#include <linux/acpi.h>
 
 #define AXP20X_OFF	0x80