ARM: 7623/1: mmc: mmci: Fixup clock gating when freq is 0 for ST-variants

In the ST Micro variant, the MMCICLOCK register must not be used to
gate the clock. Instead use MMCIPOWER register and by clearing the
PWR_ON bit to do this.

Signed-off-by: Johan Rudholm <johan.rudholm@stericsson.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>