Switch media fw hotword permission check to PermissionChecker (av)

PermissionChecker now includes some higher level logic for allowing the
HotwordDetectionService to access hotword audio.

Bug: 190011174
Test: manual - sample app can read audio (with a few other wip changes)
Change-Id: Id1b7755844c370c9465cd2180e5f03463186ef7b
1 file changed