OMAP: McBSP: Convert McBSP to platform device model

Implement McBSP as platform device and add support for
registering through platform device layer using resource
structures.

Later in this patch series, OMAP2+ McBSP driver would be modified to
use hwmod framework after populating the omap2+ hwmod database.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Acked-by: Jarkko Nikula <jhnikula@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>