Fix permission check when registering an audio policy

The current checks were allowing public apps to register an audio policy
with an APC mix as intended, but the policy could also have focus
listener and volume controller which are not intended to be used by
public apps.

Test: atest android.media.cts.AudioPlaybackCaptureTest
Bug: 129948989
Change-Id: I97d41ed08faff05e59ae6b495ee62ae11f4a09c1