mfd: twl4030-audio: Get audio MCLK via twl-core API instead of pdata

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>