powerpc/book3e-64: Move the default cpu table entry

Move the default cpu entry table for CONFIG_PPC_BOOK3E_64 to the
very end since we will probably want to support both 32-bit and
64-bit kernels for some processors that are higher up in the list.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>