ALSA: firewire-lib: cache next data_block_counter after probing tracepoints event for IR context

For debugging purpose, ALSA IEC 61883-1/6 engine has tracepoints event.
In current implementation, next data block counter is stored as current
data block counter before probing the event for IR isoc context. It's not
good to check current packet parameter.

This commit changes to assign the next data block counter after probing
the event.

Besides, Fireworks devices has a quirk to transfer isoc packet with
data block counter for the last data block. For this quirk, the
assignment is done before calling data block processing layer.

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