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.