ASoC: ad1980: Use core AC'97 reset helper

Use the new snd_ac97_reset() helper function to perform the reset and
verify the device ID.

Unfortunately the reset can't be done in snd_soc_new_ac97_codec() due to
the special requirements in order to support the non-standard 16-bit slot
mode of the ad1980.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>