powerpc: Add T4160QDS

T4160QDS shares the same platform as T4240QDS. T4160 is a low power
version of T4240, with eight e6500 cores, two DDR3 controllers, and
slightly different SerDes protocols.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>