ALSA: firewire-motu: detect SPH source of sampling clock

In MOTU FireWire series, devices have a mode to generate sampling clock
from a sequence of source packet header (SPH) included in each data block
of received packet. This mode is used for several purposes such as mode
for SMPTE time code, sync to the other sound cards and so on.

This commit adds support for the SPH mode.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20191030080644.1704-4-o-takashi@sakamocchi.jp


Signed-off-by: Takashi Iwai <tiwai@suse.de>