scsi: ufs: ufshpb: Make eviction depend on region's reads

In host mode, eviction is considered an extreme measure. Verify that the
entering region has enough reads, and the exiting region has fewer reads.

Link: https://lore.kernel.org/r/20210712095039.8093-6-avri.altman@wdc.com


Reviewed-by: Daejun Park <daejun7.park@samsung.com>
Signed-off-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>