Although CIP header is handled as context header, the length of isochronous
packet includes two quadlets for its payload. In tracepoints event the
value of payload_quadlets should includes the two quadlets. But at present
it doesn't.

This commit fixes the bug.

Fixes: b18f0cfa ("ALSA: firewire-lib: use 8 byte packet header for IT context to separate CIP header from CIP payload")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>