ALSA: hda: make snd_kcontrol_new const

Make these const as they are only passed as the 3rd argument to the
function snd_hda_gen_add_kctl, which is of type const.
Done using Coccinelle.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>