usb: android: Fix multiple issues seen with audio_source

Crash is seen when performing USB composition switch or USB cable
disconnect from audio source USB composition. Usage of
usb_remove_function() with audio_source_function_unbind_config()
results into deletion of audio source function from function list
in addition to unbind_config(). Fix this issue by removing
audio_source_function_unbind_config().

snd pcm device is also not created using snd_card_setup(). Hence
fix this issue by creating snd pcm device with audio_bind() and
removing same with audio_unbind().

Change-Id: Ia96da8b33b924952a962a7170e3604af37020931
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>