mmc: tmio: add support for the VccQ regulator

Some SD/MMC interfaces use 2 power regulators: one to power the card itself
(Vcc) and another one to pull signal lines up (VccQ). In case of eMMC and
UHS SD cards the regulators also have to be configured to supply different
voltages. The preferred order of turning supply power on and off is to
turn Vcc first on and last off.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Chris Ball <cjb@laptop.org>