ALSA: firewire-digi00x: add stream functionality

This commit adds a functionality to manage streaming.

The streaming is not controlled by CMP in IEC 61883-6. It's controlled by
IEEE 1394 write transaction to certain addresses.

Several clock sources are available, while there're no differences about
packet transmission. The value of SYT field in transmitted packets is
always zero. Thus, streams in both direction don't build synchronization.

And the device always requires received packets to transmit packets. This
driver keeps to transfer outgoing stream even if they're not required.

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