ALSA: firewire-motu: add a structure for model-dependent parameters.

MOTU FireWire series doesn't tell drivers their capabilities, thus
the drivers should have and apply model-dependent parameters to detected
models.

This commit adds a structure to represent such parameters. Capabilities
are represented by enumeration except for the number of analog line
in/out. Identification name also be in the structure because the units has
no registers for this purpose.

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