ALSA: firewire-lib: use the same unit for payload argument in tracing events

The most of tracing event in this module have the size of payload in
byte unit, however 'in_packet_without_header' event have the argument
in quadlet unit.

This commit change the unit for argument to be consistent.

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