ARM: shmobile: kzm9g: add fixed voltage regulators for SDHI0 and SDHI2

Both SDHI0 and SDHI2 power supplies on kzm9g can be switched on and off. In
the current version this is not used and the regulators are hard-wired to
"on." This patch switches SDHI0 and SDHI2 to proper fixed-voltage
regulators, using GPIOs to enable and disable them. Both ports shall
now be specifying the MMC_CAP_POWER_OFF_CARD MMC capability. Only SDHI0
has been tested with an SDIO card, since SDHI2 is a microSD slot.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>