Revert "frameworks/base: AudioPolicyManager fixes"

This reverts commit 76816eea.

There is no clear advantage associated with this change (probably it's
only useful for CAF's own libaudio), and it has at least
one disadvantage: It breaks call recording on Motorola's libaudio, which
doesn't like getting fed with a channels value like CHANNEL_IN_MONO |
CHANNEL_IN_VOICE_UPLINK.