pinctrl: Add STMFX GPIO expander Pinctrl/GPIO driver

This patch adds pinctrl/GPIO driver for STMicroelectronics
Multi-Function eXpander (STMFX) GPIO expander.
STMFX is an I2C slave controller, offering up to 24 GPIOs.
The driver relies on generic pin config interface to configure the GPIOs.

Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/pinctrl/Makefile b/drivers/pinctrl/Makefile
index 712184b..c188e0f 100644
--- a/drivers/pinctrl/Makefile
+++ b/drivers/pinctrl/Makefile
@@ -40,6 +40,7 @@
 obj-$(CONFIG_PINCTRL_LPC18XX)	+= pinctrl-lpc18xx.o
 obj-$(CONFIG_PINCTRL_TB10X)	+= pinctrl-tb10x.o
 obj-$(CONFIG_PINCTRL_ST) 	+= pinctrl-st.o
+obj-$(CONFIG_PINCTRL_STMFX) 	+= pinctrl-stmfx.o
 obj-$(CONFIG_PINCTRL_ZYNQ)	+= pinctrl-zynq.o
 obj-$(CONFIG_PINCTRL_INGENIC)	+= pinctrl-ingenic.o
 obj-$(CONFIG_PINCTRL_RK805)	+= pinctrl-rk805.o