f_audio_source: Use f_audiosource as first device name

Keep first instance name as f_audiosource and change name
for next intance as per number of instance.

Change-Id: I9888d10e1faceff16f950f20ac42261417f1d8e8
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>