regulator: cpr-regulator: add support for reading CPR fuse revision

Add support in the cpr-regulator driver for reading the CPR
fusing revision fuse parameter.  The location of this parameter
is defined using the qcom,cpr-fuse-revision device tree property.
The fusing revision value can be used on some chips in order to
determine what kind of adjustments are required.

CRs-Fixed: 762377
Change-Id: I7355c41503bbc67c5114f56060920251397abc41
Signed-off-by: David Collins <collinsd@codeaurora.org>