ALSA: oss: Release temporary buffers upon errors

ALSA: oss: Release temporary buffers upon errors

When the parameter changes fails, we don't need to keep the old
temporary buffers.  Release those (and plugin instances) upon errors
for reducing dead memory footprint.  Since we always call it at the
exit of snd_pcm_oss_changes_params_locked(), the explicit calls of
snd_pcm_oss_plugin_clear() can be dropped, too.

Along with it, unify the buffer-free calls to a single helper and call
it from the needed places.

Link: https://lore.kernel.org/r/20220318082157.29769-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>