mmc:core:put eMMC in sleep (cmd5) mode before suspend

Put MMC to sleep if it supports SLEEP/AWAKE (CMD5) in the mmc suspend
to minimize power consumption.

Signed-off-by: Balaji T K <balajitk@ti.com>
Acked-by: Venkatraman S <svenkatr@ti.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
(cherry picked from commit 3765839)

Change-Id: I0c0d5d06c4204b15471d1ca95aec0c7fcaaae816
Signed-off-by: Shruthi Krishna <skrish@codeaurora.org>