ASoC: mioa701_wm9713: Don't opencode CODEC register access

Properly use snd_soc_update_bits() instead of manually calling the CODEC
driver's read and write callbacks. The later will stop working once the
wm9713 driver has been converted to regmap.

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