mmc: core: Remove redundant mmc_power_up|off at runtime callbacks

Commit "mmc: core: Push common suspend|resume code into each bus_ops"
moved the responsibility for doing mmc_power_up|off into each
suspend/resume bus_ops. When using MMC_CAP_AGGRESSIVE_PM, through the
runtime callbacks, calls to mmc_power_up|off became redundant.

When removing them, we are also able to remove the calls to
mmc_claim|release_host, thus simplifing code a bit more.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>