power: supply: axp20x: add missing include bitops.h

The axp20x_usb_power driver uses BIT() operations but lacks the include
for it. Include the bitops.h header file.
Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>
Signed-off-by: Priit Laes <plaes@plaes.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/axp20x_usb_power.c

@@ -10,6 +10,7 @@
  * option) any later version.
  */
 
+#include <linux/bitops.h>
 #include <linux/device.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>