ASoC: sun8i-codec: Add the AIF3 DAI, widgets, and routes

AIF3 has some differences from AIF1 and AIF2:
 - It supports one channel only
 - It supports master mode only
 - It is not directly connected to any of the mixers; instead all audio
   goes through a mux with AIF2.
 - It does not have its own clock dividers; instead it reuses AIF2 BCLK
   and LRCK. This means that when both AIF2 and AIF3 are active, they
   must use the same sample rate and total frame width. Since AIF2 and
   AIF3 are only used for codec2codec DAI links, constraints are not
   applicable here; the only thing we can do when the rates don't match
   is report an error.

Make the necessary adjustments to support this AIF.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-18-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>