ALSA: firewire-lib: Add 'direction' member to 'cmp_connection' structure

This patch adds 'direction' member to 'cmp_connection' structure to indicate
the direction of connection. This patch also adds 'direction' argument to
cmp_connection_init() function to determine the direction.

The cmp_connection_init() function is exported and used in snd-firewire-speakers
so this patch also affect it.

This patch just add them. Actual implementation will be done by followed
patches.

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