usb: gadget: f_uac2: allow changing terminal types through configfs

Add "c_terminal_type" and "p_terminal_type" configfs entries
in order to allow the user to change the capture and playback terminal
type codes.

These fields affect the type of audio device that Windows detects, so
being able to modify this is useful when it would be advantageous for
a gadget to be detected as something other than a generic
speaker/microphone.

The fields default to microphone for the capture type field and speaker
for the playback type field as was the case before.

Signed-off-by: James Gruber <jimmyjgruber@gmail.com>
Link: https://lore.kernel.org/r/20230914222746.155126-1-jimmyjgruber@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>