ARM: ux500: implement pin API

Implement an API to allow a list of pincfgs to be remuxed to active
and sleep modes, for power saving. This is not exported on purpose,
because it is not to be called by drivers directly.

Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Reviewed-by: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>