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.

Reference:
15209ec: mmc: Add long power off notification support
62c8dce: mmc: core: Update PON based on the system state.

Change-Id: Ib842c6fd9569c66348a467f7059e84b9320d2b77
Signed-off-by: Ram Prakash Gupta <rampraka@codeaurora.org>