[POWERPC] 4xx: Add 405EXr to cputable

This patch adds the 405EXr to the powerpc cuptable. Basically the 405EXr
is a 405EX with only one EMAC and only one PCIe interface.

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>