PowerManagerService: Log when proximity blocks wake

There is currently no indication when the proximity sensor
is allowed to prevent the system from waking up.  This can
make it hard to debug weird failed wakes.  Add a log to
facilitate debugging wakup problems.

Change-Id: I7df34e13b1268a4e7211fb06ccd88f2053c0af0a
(cherry picked from commit 21ddba54)