arm, config: Add an example ARM big.LITTLE(tm) configuration script
An ARM big.LITTLE system consists of two cpu clusters: the big

CPUs are typically complex out-of-order cores and the little

CPUs are simpler in-order ones. The fs_bigLITTLE.py script

can run a full system simulation with various number of big

and little cores and cache hierarchy. The commit also includes

two example device tree files for booting Linux on the

bigLITTLE system.
Change-Id: I6396fb3b2d8f27049ccae49d8666d643b66c088b

Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>