MFD: twl4030-codec: APLL_INFREQ handling in the MFD driver

Configure the APLL_INFREQ field in the APLL_CTL register
based on the platform data.
Provide also a function for childs to query the audio_mclk
frequency.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>