bebob/oxfw: expand bytes for model name

Griffin FireWave has 'Griffin FireWave Surround'(26 bytes) for model
name in its Config ROM. But current code keep 24 bytes and strip
the name.

This is reported:
http://mailman.alsa-project.org/pipermail/alsa-devel/2014-February/073145.html

Here use 32 bytes because 'struct snd_card.shorname' is char[32].