ALSA: hda - VIA: Fix codec type for VT1708BCE at the right timing

Add get_codec_type() in via_new_spec() function to make sure getting
correct codec type before building mixer controls.

Signed-off-by: Lydia Wang <lydiawang@viatech.com.cn>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>