twl-core has API to get the boot time configured HFCLK rate which has the
same rate as the audio MCLK.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com> Acked-by: Samuel Ortiz <sameo@linux.intel.com> Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>