mmc: sdhci-msm: Add support for UHS cards

Enabling support for ultra high speed mode cards requires some
voltage switching and interaction with the PMIC via a special
power IRQ. Add support for this.

Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>