regulator: cpr3-regulator: stop CPRh controller registration if initialized

Stop the registration of a CPRh type cpr3-regulator controller if
CPRh has already been initialized by the boot loader.  This
ensures that boot loader control of CPRh can be implemented
independently of further cpr3-regulator driver or device tree
changes.

Change-Id: I080511b5670f6cd34ee29d0ff97ccc59f67231a9
Signed-off-by: David Collins <collinsd@codeaurora.org>