Add single register pin controller driver

This patch adds a pin controller driver supporting devices
using a single configuration register per pin.
Signed-off-by: Felix Brack <fb@ltec.ch>
diff --git a/drivers/pinctrl/Makefile b/drivers/pinctrl/Makefile
index b04ca86..2ac9c19 100644
--- a/drivers/pinctrl/Makefile
+++ b/drivers/pinctrl/Makefile
@@ -16,5 +16,6 @@
 obj-$(CONFIG_PINCTRL_EXYNOS)	+= exynos/
 obj-$(CONFIG_PINCTRL_MESON)	+= meson/
 obj-$(CONFIG_PINCTRL_MVEBU)	+= mvebu/
+obj-$(CONFIG_PINCTRL_SINGLE)	+= pinctrl-single.o
 obj-$(CONFIG_PINCTRL_STI)	+= pinctrl-sti.o
 obj-$(CONFIG_PINCTRL_STM32)	+= pinctrl_stm32.o