mmc: add timer to issue flush request periodically

mmc: add timer to issue flush request periodically

-Added timer for issuing flush requests periodically
to reduce the cache flush overhead during read/write
data transfers on eMMC device.
-Flush timer will be deleted and resumed back during
device suspend/resume calls.

Bug 200165213

Change-Id: Iac6199922bc82cbc9394f0a6b3c6067283ed5240
Reviewed-on: http://git-master/r/930061

Signed-off-by: R Raj Kumar <rrajk@nvidia.com>
Change-Id: I42ccba5b7ebaa9495817406bbd66312a9a4fea9c
Reviewed-on: http://git-master/r/1171079
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Venu Byravarasu <vbyravarasu@nvidia.com>