ALSA: ctl: fix a bug to return no identical information in info operation for userspace controls

In operations of SNDRV_CTL_IOCTL_ELEM_INFO, identical information in
returned value is cleared. This is not better to userspace application.

This commit confirms to return full identical information to the
operations.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>