mmc: core: add support for devfreq suspend/resume

This change adds use of devfreq suspend/resume API.
In the current version of the code, devfreq is fully brought
up/down on each runtime resume/suspend which causes
statistics loss and is time consuming.
This change addresses the above by adding support for
devfreq suspend/resume to be called on each system
suspend/resume, runtime suspend/resume, power restore.

Change-Id: Id209826fb9499084ae96c7d3a47e4032326f61e9
Signed-off-by: Talel Shenhar <tatias@codeaurora.org>