mmc: mmci: Move ios_handler functionality into the driver

There are currently two instances of the ios_handler being used.
Both of which mearly toy with some regulator settings. Now there
is a GPIO regulator API, we can use that instead, and lessen the
per platform burden. By doing this, we also become more Device
Tree compatible.

Acked-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>