pinctrl: imx: work around select input quirk

pinctrl: imx: work around select input quirk

The select input for some pin may not be implemented using the regular
select input register but the general purpose register.  A real example
is that imx6q designers found the select input for USB OTG ID pin is
missing at the very late stage, and can not add a new select input
register but have to use a general purpose register bit to implement it.

The patch adds a workaround for such select input quirk by interpreting
the input_val cell of pin function ID in a different way, so that all
the info that needed for setting up select input bits in general purpose
register could be decoded from there.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Tested-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>