[ALSA] vx - Fix memory leak on error path

Modules: Digigram VX core

Noticed by Eric Sesterhenn on kernel-janitors@

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>