typhoon: get rid of redundant conditional before all to release_firmware()

There's no need to test for a NULL pointer before calling
release_firmware() since the function does that check itself, so
remove the redundant test.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Acked-by: David Dillow <dave@thedillows.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>