mmc: sdhci: Move sdhci_runtime_pm_bus_off|on() to avoid pre-definition

There are no need to have two versions of sdhci_runtime_pm_bus_off|on(),
depending on whether CONFIG_PM is set or unset. Thus it's easy to move the
implementation of these functions a bit earlier to avoid the unnecessary
pre-definition of them, so let's do that.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>