pinctrl: pinctrl-imx: add imx pinctrl core driver

The driver has mux and config support while the gpio is still
not supported.
For select input setting, the driver will handle it internally
and do not need user to take care of it.

The pinctrl-imx core driver will parse the dts file and dynamically
create the pinmux functions and groups.

Each IMX SoC pinctrl driver should register pins with a pin register map
including mux register and config register and select input map to core
for proper operations.

Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>