[PATCH] Use PVR to distinguish MPC5200B from MPC5200 in boot message

MPC5200B systems are incorrectly reported as MPC5200 in U-Boot start-up
message. Use PVR to distinguish between the two variants, and print proper CPU
information.

Signed-off-by: Grzegorz Wianecki <grzegorz.wianecki@gmail.com>
Signed-off-by: Bartlomiej Sieka <tur@semihalf.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>