drivers: gpio: implement PALMAS GPIO cell

Add gpio driver for TI Palmas series PMIC. This has 8 gpio which can
work as input/output.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index dab3eb9..da3da5d 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -55,6 +55,7 @@
 obj-$(CONFIG_HIKEY_GPIO)	+= hi6220_gpio.o
 obj-$(CONFIG_HSDK_CREG_GPIO)	+= hsdk-creg-gpio.o
 obj-$(CONFIG_IMX_RGPIO2P)	+= imx_rgpio2p.o
+obj-$(CONFIG_$(SPL_)PALMAS_GPIO)	+= palmas_gpio.o
 obj-$(CONFIG_PIC32_GPIO)	+= pic32_gpio.o
 obj-$(CONFIG_OCTEON_GPIO)	+= octeon_gpio.o
 obj-$(CONFIG_MVEBU_GPIO)	+= mvebu_gpio.o