ASoC: sunxi: sun4i-codec: drop SNDRV_PCM_RATE_KNOT

The custom rate constraint lists was necessary to support 12kHz and 24kHz.
These rates are now available through SNDRV_PCM_RATE_12000 and
SNDRV_PCM_RATE_24000.

Use them and drop the custom rate constraint rule.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: David Rhodes <drhodes@opensource.cirrus.com>
Acked-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20240905-alsa-12-24-128-v1-11-8371948d3921@baylibre.com