mmc: tmio: fix power-mode interpretation

The power-mode sequence on MMC is MMC_POWER_OFF -> MMC_POWER_UP ->
MMC_POWER_ON and not MMC_POWER_ON -> MMC_POWER_UP, as the driver currently
is implying.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Chris Ball <cjb@laptop.org>