ARM: 5666/1: Revamped U300 padmux API

This abstracts the hackish padmux API on the U300 platform into
something more manageable. It provides a way for drivers to
activate/deactivate a certain padmux setting. It will also switch
the users of the old API over to using the new style, pushing
muxing into the apropriate setup files.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>