Strip some code by letting the mmc core handle the regulators. The old
.gpio_power pdata handling is kept around for now.

This also set the voltage on the regulator and handles -EPROBE_DEFER
correctly.
Signed-off-by: NDaniel Mack <daniel@zonque.org>
Acked-by: NRobert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>