ALSA: usb-audio: Quirk for BOSS GT-001

The capture stream of BOSS GT-001 seems always requiring to be tied
with the playback stream.  OTOH, the playback stream of BOSS GT-01
doesn't seem working in the implicit fb mode, since the playback must
be running before the capture stream.

This patch tries to address the points above:
- Avoid the implicit fb mode for the playback
- Set up a fake sync EP for the capture stream with the hard-coded
  playback stream using the implicit fb mode

Reported-by: Keith Milner <kamilner@superlative.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>