mpc86xx; Write MAC address to mac-address and local-mac-address

Some device trees have a mac-address property, some have local-mac-address,
and some have both.  To support all of these device trees, ftp_cpu_setup()
should write the MAC address to mac-address and local-mac-address, if they
exist.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Jon Loeliger <jdl@freescale.com>