msm: ais: allow sensor power down from init state

Allow sensor power down from init state to facilitate requirement of
ensuring all sensors are powered off first in some usecases due to
dependencies in power up and detect sequences.

Change-Id: Iac003a4475ac3925c00202574a02f1d2c761a202
Signed-off-by: Terence Ho <terenceh@codeaurora.org>