ARM: ux500: Specify the ux5x0 MMCI regulator's on/off GPIO as high-enable

If not specified, the GPIO control bit is inverted by default i.e.
low-enable and high-disable. This is not the case with the MMCI
regulator, hence it will turn on during a disable and off when
regulator_enable() is invoked.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>