[ALSA] continue on IS_ERR from platform device registration

Continue with the next one on error from device registration.

This would seem the correct thing to do, even if it's not the probe()
error that we're getting.

Signed-off-by: Rene Herman <rene.herman@keyaccess.nl>
Signed-off-by: Takashi Iwai <tiwai@suse.de>