ASoC: sun8i-codec: Fix ADC_DIG_CTRL field name

This is the enable bit for the "AD"C, not the "DA"C.

Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20200831034852.18841-6-samuel@sholland.org
Signed-off-by: Mark Brown <broonie@kernel.org>