ufs: tune bkops while power managment events

Add capability to control the auto bkops during suspend.
If host explicitly enables the auto bkops (background operation) on device
then only device would perform the bkops on its own. If auto bkops is not
enabled explicitly and if the device reaches to state where it must do
background operation, device would raise the urgent bkops exception event
to host and then host will enable the auto bkops on device. This patch
adds the option to choose whether auto bkops should be enabled during
runtime suspend or not. Since we don't want to keep the device active to
perform the non critical bkops, host will enable urgent bkops only.

Keep auto-bkops enabled after resume if urgent bkops needed.
If device bkops status shows that its in critical need of executing
background operations, host should allow the device to continue doing
background operations.

Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Dolev Raviv <draviv@codeaurora.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>