ASoC: es8328: Set symmetric rates

Although the ES8328 does support different rates for capture and
playback, only very limited combinations are supported (8kHz and 48kHz
or 8.0182kHz and 44.1kHz) with most rates required to be symmetric.

Instead of adding a lot of complexity for little gain, let's enforce
symmetric rates.

Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Mark Brown <broonie@kernel.org>