mmc: core: Fix power_off_notify during suspend

The eMMC 4.5 devices respond to only RESET and AWAKE command in the
sleep state. Hence the mmc switch command to notify power off state
should be sent before the device enters sleep state.

This patch fixes the same.

Signed-off-by: Girish K S <girish.shivananjappa@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>