BACKPORT: FROMGIT: scsi: ufs: Add write booster feature support

The write performance of TLC NAND is considerably lower than SLC NAND.
Using SLC NAND as a WriteBooster Buffer enables the write request to be
processed with lower latency and improves the overall write performance.

Adds support for shared-buffer mode WriteBooster.

WriteBooster enable: SW enables it when clocks are scaled up, thus it's
enabled only in high load conditions.

WriteBooster disable: SW will disable the feature, when clocks are scaled
down. Thus writes would go as normal writes.

To keep the endurance of the WriteBooster Buffer at a maximum, this
load-based toggling is adopted.

Bug: 157166850
(cherry picked from commit 3d17b9b5ab11556b2fea07d4f24154095a685ad2
https://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git 5.8/scsi-queue)
Link:https://lore.kernel.org/r/2871444d9083b0e9323ef6d8ff1b544b7784adc9.1587591527.git.asutoshd@codeaurora.org


Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Change-Id: I91612bc379520aa756eae5120ef214d34d5ed0c4
Signed-off-by: Can Guo <cang@codeaurora.org>