FROMGIT: scsi: ufshpb: Verify that num_inflight_map_req is non-negative

num_inflight_map_req should not be negative.  It is incremented and
decremented without any protection, allowing it theoretically to be
negative, should some weird unbalanced count occur.

Verify that the those calls are properly serielized.

Link: https://lore.kernel.org/r/20210808090024.21721-4-avri.altman@wdc.com


Fixes: 33845a2d (scsi: ufs: ufshpb: Limit the number of in-flight map requests)
(cherry picked from commit 22aede9f
git: //git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git for-next)
Signed-off-by: Avri Altman <avri.altman@wdc.com>
Change-Id: I8a8252c919e6678752b60bcd950cb08e765e6aed