cnss2: Update CPR voltage after comparing with BT CxMx voltage

As per requirement, the final CPR voltage being updated to RPMh
should be the larger one between the one sent from firmware and
BT CxMx which is a fixed value voltage.

Change-Id: I095cb30b3f82c50895af449e40950e88fa5fa874
Signed-off-by: Yue Ma <yuem@codeaurora.org>