mmc: Add long power off notification support

At the moment only POWER_OFF_SHORT is sent to the device in case the host
is suspended. This patch adds the support of sending POWER_OFF_LONG
notification in case the device is powered off.

According to device vendors the POWER_OFF_LONG notification will shorten
the initialization time of the eMMC card during next boot up.

Change-Id: I3c6f224398450cf10463cbb316613fd430d1e8d2
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>