ALSA: firewire-lib: add a kernel API to stop a couple of AMDTP streams in AMDTP domain

This commit adds a kernel API to stop a couple of isochronous contexts
for AMDTP streams. The API is not protected with any lock primitive.
Callers should use this with enough lock against concurrent access.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>