snd-fireworks: change to blocking mode

Fireworks's output stream is in blocking mode. To handle nodata packet,
this commit change its mode from previous non-blocking mode.

commit 5a13554864aba19737e5a1708b70c596f03cf17f is named as "snd-fireworks:
add blocking mode" but this is a typo for "snd-firewire-lib: support
blocking mode".