ALSA: firewire-lib: code refactoring for error path of parser for CIP header

When a parser for CIP header returns -EAGAIN, no extra care is needed
to probe tracepoints event.

This commit adds code refactoring for the error path.

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