mmc: sdhci: move regulator handling into sdhci_set_power()

Move the regulator handling into sdhci_set_power() rather than being in
sdhci_do_set_ios().  This wraps all power control up into this function.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Tested-by: Markus Pargmann <mpa@pengutronix.de>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <chris@printf.net>