ASoC: SOF: add a helper to get topology configured mclk

Add helper sof_dai_ssp_mclk to get the topology configured MCLK from a
pcm_runtime, return 0 if it is not available, and error if the dai type
is not SSP at the moment.

Export the helper for external use, e.g. from machine drivers.

Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Reviewed-by: Daniel Baluta <daniel.baluta@gmail.com>
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20210319124950.3853994-1-kai.vehmanen@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>