pinctrl: pinctrl-imx: add imx51 pinctrl driver

ChangeLog v1->v2:
* change PIN_FUNC_ID base in binding doc to 0 from 1.

Acked-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/pinctrl/Kconfig b/drivers/pinctrl/Kconfig
index 173b71d..91c1f64 100644
--- a/drivers/pinctrl/Kconfig
+++ b/drivers/pinctrl/Kconfig
@@ -31,6 +31,14 @@
 	select PINMUX
 	select PINCONF
 
+config PINCTRL_IMX51
+	bool "IMX51 pinctrl driver"
+	depends on OF
+	depends on SOC_IMX51
+	select PINCTRL_IMX
+	help
+	  Say Y here to enable the imx51 pinctrl driver
+
 config PINCTRL_IMX53
 	bool "IMX53 pinctrl driver"
 	depends on OF