msm: cpr: Use NOTIFY_OK to return the success from notifier callback

0x0 return code points to NOTIFY_DONE which means the Don't care
condition, which is used while returning from the notifier callback
with conditions which doesn't suit. If we are returning success
from the notifier then it should be NOTIFY_OK.

Change-Id: I957069ea342dfdeb729a4181808c8ecaba97df1e
Signed-off-by: Trilok Soni <tsoni@codeaurora.org>