RealView: Move more device address definitions to board-eb.h

The upcoming PB11MPCore and PB1176 have different memory maps and some
of the definitions in platform.h are no longer common. This patch
moves them to the board-eb.h file and updates their usage in
realview_eb.c.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>