pinctrl: freescale: imx: add shared input select reg support

- Add shared input select register support
- imx7d has two iomux controllers iomuxc and iomuxc-lpsr
  which share select_input register for daisy chain settings

Signed-off-by: Adrian Alonso <aalonso@freescale.com>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>