ASoC: sun4i-i2s: Add support for H6 I2S

H6 I2S is very similar to that in H3, except it supports up to 16
channels.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Marcus Cooper <codekipper@gmail.com>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Clément Péron <peron.clem@gmail.com>
Link: https://lore.kernel.org/r/20201030144648.397824-4-peron.clem@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>