PLAT: OMAP: Modifications at devices.c and mmc.h to use multislot structures

Modifications at arch/arm/plat-omap/devices.c and include/asm-arm/arch-omap/mmc.h
to use multislot structures.

Signed-off-by: Carlos Eduardo Aguiar <carlos.aguiar@indt.org.br>
Signed-off-by: Felipe Balbi <felipe.lima@indt.org.br>
Signed-off-by: Jarkko Lavinen <jarkko.lavinen@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>