powerpc/85xx: Fix FSL RapidIO probing on MDS boards

FSL RapidIO won't probe without a proper compatible entry. This
patch fixes the issue by adding fsl,rapidio-delta compatible to
mpc85xx_ids.

Signed-off-by: Randy Vinson <rvinson@mvista.com>
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>