The OMAP2+ variant of McASP is different from Davinci variant w.r.to
some register offset.

Changes
- Add new MCASP_VERSION_3 to identify new variant. New DT compatible
  "ti,omap2-mcasp-audio" to identify version 3 controller.
- The register offsets are handled depending on the version.

Note:
    DMA parameters (dma fifo offset) are not updated and will be done later.
Signed-off-by: NHebbar, Gururaja <gururaja.hebbar@ti.com>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>