regulator: cpr-regulator: disable all debug printing by default

Recent targets trigger many CPR interrupts while in steady state.
This results in a huge amount of noise in the kernel log since
CPR interrupt messages are printed by default.  Change the
default behavior so that no CPR debug messages are printed.

It is still possible to re-enable cpr-regulator debug printing
at runtime from userspace if necessary.

Change-Id: I24227c08c27e1039278a36d758463bcdd78b93aa
Signed-off-by: David Collins <collinsd@codeaurora.org>