powerpc/fsl-booke: Add e55xx (64-bit) smp defconfig

The p5020 SoC from Freescale is the first 64-bit Book-E processor and
utilizes the two e5500 cores.  Adding a defconfig that enables basic kernel
for e5500 based processors.

Also added the p5020 / e5500 support to the ppc64e defconfig.

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