arm, config: added support for ex5 model of big.LITTLE

arm, config: added support for ex5 model of big.LITTLE

This patch enables using calibrated big and LITTLE cores, ex5_big and
ex5_LITTLE instead of the default 'arm_detailed' and 'minor' cpus. The ex5
model is based on the Samsung Exynos 5 Octa (5422) SoC. Operation and memory
hierarchy latencies have been calibrated using the lmbench micro-benchmark
suite. The preliminary validation results have been published as: 'Full-System
Simulation of big.LITTLE Multicore Architecture for Performance and Energy
Exploration', in International Symposium on Embedded Multicore/Many-core
Systems-on-Chip (MCSoC'16), Lyon, France (Sep, 2016).

From http://reviews.gem5.org/r/3666

Change-Id: I4935dee0a9222bd1bf7adfccb9443014945bb2d7
Signed-off-by: Anastasiia Butko <abutko@lbl.gov>
Signed-off-by: Pierre-Yves Péneau <pierre-yves.peneau@lirmm.fr>
Reviewed-on: https://gem5-review.googlesource.com/2464
Reviewed-by: Gabor Dozsa <gabor.dozsa@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>