ALSA: hda/via - Simplify control management

This patch replaces the control element creations in VIA codec driver
with the standard snd_hda_gen_add_kctl() calls as a cleanup.  There
are two major fields targeted by this patch: the beep controls and
static init controls.

The former is converted just like other codec drivers do.  The
spec->beep_amp field can be eliminated by this change as well.

The latter, static init controls, are replaced simply with explicit
snd_hda_gen_add_kctl() calls.

After these conversions, via_build_controls() becomes superfluous and
replaced with snd_hda_gen_build_controls(), too.

Signed-off-by: Takashi Iwai <tiwai@suse.de>