regulator: cpr-regulator: make CPR scheme fuse checking optional

The CPR scheme fuse bit is used for indicating if a global or local
target scheme is used for CPR. It will be eliminated on some future
devices.

Make the "qcom,cpr-fuse-bp-scheme" property optional to allow the
future devices without a scheme fuse bit to boot up successfully.

Change-Id: I892e763a0875ec8a5abec8798485defae9b3252b
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>