ASoC: sun4i-codec: Rename some sun7i-only registers

Some of the registers defined in the driver are only usable on the
A20. Rename these registers.

Signed-off-by: Danny Milosavljevic <dannym@scratchpost.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>