ARM: ux500: Enable GPIO regulator for SD-card for snowball

Fixes: c94a4ab7

 ("ARM: ux500: Disable the MMCI gpio-regulator by default")
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>