USB: f_uac2: Update terminal types as mic and speaker

Update input and output terminal types as microphone and speaker
to advertise to host as part of descriptors during USB enumeration.

Change-Id: I5338394ce9fe3bb783f3b0dd8bede3c66dbc8750
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>