ARM: OMAP: McBSP: Prepare for splitting into omap1 and omap2 code

This patch transform mcbsp code to use platform data
from arch/arm/plat-omap/devices.c

It also gets ride of ifdefs on mcbsp.c code.
To do it, a platform data structure was defined.

Signed-off-by: Eduardo Valentin <eduardo.valentin@indt.org.br>
Signed-off-by: Tony Lindgren <tony@atomide.com>