mmc: core: add partial initialization support

This change adds the ability to partially initialize
the MMC card by using card Sleep/Awake sequence (CMD5).
Card will be sent to Sleep state during runtime/system suspend
and will be woken up during runtime/system resume.
By using this sequence the card doesn't need full initialization
which gives time reduction in system/runtime resume path.

Change-Id: Id8dadf03ef4226f7c4675fadbacac7bb15c0289e
Signed-off-by: Talel Shenhar <tatias@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>