powerpc: Add a new zImage for maple using a different link address

The maple platform failed to load because it's firmware could not take a
link address of 0x4000000.  A new platform type with a link address of
0x400000 had to be created for the maple.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>