PINCTRL: stm32f7: add pin control driver

This driver uses the same pin control binding as that of linux, binding
document of this patch is copied from linux. One addition done is for
GPIO input and output mode configuration which was missing.

Signed-off-by: Vikas Manocha <vikas.manocha@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pinctrl/Makefile b/drivers/pinctrl/Makefile
index a2f8101..b04ca86 100644
--- a/drivers/pinctrl/Makefile
+++ b/drivers/pinctrl/Makefile
@@ -17,3 +17,4 @@
 obj-$(CONFIG_PINCTRL_MESON)	+= meson/
 obj-$(CONFIG_PINCTRL_MVEBU)	+= mvebu/
 obj-$(CONFIG_PINCTRL_STI)	+= pinctrl-sti.o
+obj-$(CONFIG_PINCTRL_STM32)	+= pinctrl_stm32.o