ASoC: omap-mcbsp: Create a single driver for McBSP

The OMAP McBSP driver stack used to contain two different
drivers. One of them was used as kind low-level access to
the IP, while the other driver was the ASoC DAI driver.
There were global, shared structures, in different places,
the McBSP instances are reffered with id numbers (sometimes
0 based, in other cases 1 based id numbers).

Create one single driver for OMAP McBSP with name: omap-mcbsp.
Convert the old omap-mcbsp driver initially to be a library
for the omap-mcbsp DAI driver. With this change we can get rid
of all global variables, structures.

Further cleanup is coming...

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: Grazvydas Ignotas <notasas@gmail.com>
Tested-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Signed-off-by: Liam Girdwood <lrg@ti.com>