[ALSA] Return error if no user TLV is defined

Retrun error to user TLV_READ ioctl if no TLV is defined.
(Until now, nothing was written and rerunred successfully.)

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>