ASoC: sun4i-codec: Remove redundant SND_PCM_RATE_KNOT

The SND_PCM_RATE_KNOT covers all the rate settings, even though some that
we don't support, while we also list all the rate we support. Simply remove
it.

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