scsi: ufs: Optimize the command queueing code

scsi: ufs: Optimize the command queueing code

Remove the clock scaling lock from ufshcd_queuecommand() since it is a
performance bottleneck. Instead check the SCSI device budget bitmaps in the
code that waits for ongoing ufshcd_queuecommand() calls. A bit is set in
sdev->budget_map just before scsi_queue_rq() is called and a bit is cleared
from that bitmap if scsi_queue_rq() does not submit the request or after
the request has finished. See also the blk_mq_{get,put}_dispatch_budget()
calls in the block layer.

There is no risk for a livelock since the block layer delays queue reruns
if queueing a request fails because the SCSI host has been blocked.

Link: https://lore.kernel.org/r/20211203231950.193369-17-bvanassche@acm.org
Cc: Asutosh Das (asd) <asutoshd@codeaurora.org>
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>