audioflinger: changes for new audio devices enums

The ThreadBase class now has a separate member for input
and output devices (mInDevice, mOutDevice).

Only query get_supported_devices() from audio HAL if the function
is exposed and if the audio policy manager did not specify the
audio module to open.

Also fixed bug in AEC preprocessing that would reset
to default output device when an input device was given.

Change-Id: I19d4d06aeb920b068e3ef31e6e6be6345ce5d67a