ASoC: omap-mcbsp: Re-arrange files for core McBSP and Sidetone function split

The mcbsp.c was copied a while back from arch/arm/plat-omap/mcbsp.c and it
contained a mix of McBSP and McBSP sidetone functions.

Create new file structure with the following split:
omap-mcbsp.c - McBSP related functions
omap-mcbsp-st.c - McBSP sidetone functionality
omap-mcbsp-priv.h - Private header for internal use
omap-mcbsp.h - Header for user drivers

I have tried to do the code move with minimal code change, cleanup patches
can be based on the new structure.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Tested-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Peter Ujfalusi

sound/soc/omap/Makefile

@@ -2,7 +2,7 @@
 # OMAP Platform Support
 snd-soc-sdma-objs := sdma-pcm.o
 snd-soc-omap-dmic-objs := omap-dmic.o
-snd-soc-omap-mcbsp-objs := omap-mcbsp.o mcbsp.o
+snd-soc-omap-mcbsp-objs := omap-mcbsp.o omap-mcbsp-st.o
 snd-soc-omap-mcpdm-objs := omap-mcpdm.o
 snd-soc-omap-hdmi-audio-objs := omap-hdmi-audio.o