aaudio_loopback: Allow specifying input device id

This is useful when there are multiple audio devices in the system.

Test: use aaudio_loopback on a TV device with USB soundcard connected
      specify -d<HDMI out device id> -D<USB in device id>

Change-Id: I60e84132f5974db6f4314c58f76705018e22b7db
1 file changed