scsi: ufs: Check boundary condition on pm qos active_reqs

OEMs implement their own UFS features based on QCOM's
UFS infrastructure, and they can call UFS PM QoS interfaces
from their code.

Adding boundary condition for active_reqs will help to
catch and throw warning in case of any abnormality.

Change-Id: Ibd9d3b5c5bde2260ec08d48ba858c4f3b7ff0d9d
Signed-off-by: Nitin Rawat <nitirawa@codeaurora.org>