mfd: Add support for Device Tree to twl6040

Device tree based probing support for the core twl6040 driver. Child
devices will be created as MFD devices:
- ASoC codec is always created
- Vibra child is only created if the vibra section present in the DT blob.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>