mmc: core: move the cache disabling operation to mmc_suspend

Cache control is an eMMC feature and in therefore should be
part of MMC's bus resume operations, performed in mmc_suspend,
rather than in the generic mmc_suspend_host().

Signed-off-by: Maya Erez <merez@codeaurora.org>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>