ALSA: firewire-lib: fix different data block counter between probed event and...

ALSA: firewire-lib: fix different data block counter between probed event and transferred isochronous packet

For IT context, tracepoints event is probed after calculating next data
block counter. This brings difference of data block counter between
the probed event and actual isochronous packet.

This commit fixes it.

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