ASoC: sunxi: sun50i-codec-analog: Rename hpvcc regulator supply to cpvdd

The A64 datasheet lists the supply rail for the headphone amp's charge
pump as "CPVDD". cpvdd-supply is the name of the property for this power
rail specified in the device tree bindings. "HPVCC" was the name used in
the A33 datasheet for the same function.

Rename the supply so it matches the datasheet, bindings, and the subject
from the original commit.

Fixes: ca0412a0 ("ASoC: sunxi: sun50i-codec-analog: Add support for cpvdd regulator supply")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Mark Brown <broonie@kernel.org>