ALSA: oxfw: allocate own address region for SCS.1 series

When physical controls on SCS.1 models are operated, the models transfer
MIDI messages in asynchronous transactions on IEEE 1394 bus. The models
have a register to have an address for the transactions, and drivers
can register own address for this purpose.

This commit keeps a region of address, registers it and adds a handler for
the transactions.

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