ARM: OMAP: mcbsp: Convert core driver to proper platform driver

Convert the plat-omap/mcbsp.c driver to be proper platform driver.
Remove the omap_mcbsp_init function call which was called from
mach-omap1/2/mcbsp.c to register the platform driver for the just
created platform device in the same function.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Grazvydas Ignotas <notasas@gmail.com>
Tested-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Acked-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Signed-off-by: Liam Girdwood <lrg@ti.com>