ALSA: hda - Handle a few verbs as read-only

Although they can be written, handle a few verbs as read-only in
regmap interface: CONFIG_DEFAULT, CONV and CVT_CHAN_COUNT.  These are
either updated in PCM or HDMI management code in a volatile manner, or
just needed only as parameter, thus they don't need to be written at
resume sync.

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