drivers: gpio: implement MAX77663 GPIO cell

MAXIM Semiconductor's PMIC, MAX77663 has 8 GPIO pins and 3 GPIO-like
pins. It also supports interrupts from these pins.

Add GPIO driver for these pins to control via GPIO APIs.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
diff --git a/include/power/max77663.h b/include/power/max77663.h
index b3ae3da..fcb5916 100644
--- a/include/power/max77663.h
+++ b/include/power/max77663.h
@@ -13,6 +13,7 @@
 #define MAX77663_LDO_DRIVER		"max77663_ldo"
 #define MAX77663_SD_DRIVER		"max77663_sd"
 #define MAX77663_RST_DRIVER		"max77663_rst"
+#define MAX77663_GPIO_DRIVER		"max77663_gpio"
 
 /* Step-Down (SD) Regulator calculations */
 #define SD_STATUS_MASK			0x30