ASoC: Intel: sof_cs42l42: use helper function to get bclk frequency

ASoC: Intel: sof_cs42l42: use helper function to get bclk frequency

Use sof_dai_get_bclk() function to get bclk frequency instead of a
hard-coded magic number depending on configuration in topology.

Reviewed-by: Bard Liao <bard.liao@intel.com>
Signed-off-by: Brent Lu <brent.lu@intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210625205042.65181-5-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>