powerpc/85xx: mpc8548cds - Add RapidIO node to dts

Enable RapidIO and add rapidio and rmu nodes to dts.

Signed-off-by: Zhao Chenhui <chenhui.zhao@freescale.com>
Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>