pinctrl: at91: add pinctrl driver

AT91 PIO controller is a combined gpio-controller, pin-mux and
pin-config module. The peripheral's pins are assigned through
per-pin based muxing logic.

Each SoC will have to describe the its limitation and pin
configuration via device tree. This will allow to do not need
to touch the C code when adding new SoC if the IP version is
supported.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pinctrl/Makefile b/drivers/pinctrl/Makefile
index 2ac9c19..bbb2480 100644
--- a/drivers/pinctrl/Makefile
+++ b/drivers/pinctrl/Makefile
@@ -5,6 +5,7 @@
 obj-y					+= pinctrl-uclass.o
 obj-$(CONFIG_$(SPL_)PINCTRL_GENERIC)	+= pinctrl-generic.o
 
+obj-$(CONFIG_PINCTRL_AT91)		+= pinctrl-at91.o
 obj-$(CONFIG_PINCTRL_AT91PIO4)		+= pinctrl-at91-pio4.o
 obj-y					+= nxp/
 obj-$(CONFIG_ARCH_ATH79) += ath79/