mmc: tmio: add regulator support

Currently the TMIO MMC driver derives the OCR mask from the platform data
and uses a platform callback to turn card power on and off. This patch adds
regulator support to the driver.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Cc: Liam Girdwood <lrg@ti.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Chris Ball <cjb@laptop.org>