configs: Use absolute import paths

Use absoluate import paths to be Python 3 compatible. This also
imports absolute_import from __future__ to ensure that Python 2.7
behaves the same way as Python 3.

Change-Id: Ica06ed95814e9cd3e768b3e1785075e36f6e56d0
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/16708
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

config, arm: Unify checkpoint path handling in bL configs

The vanilla bL configuration file and the dist-gem5 configuration file
use slightly different code paths when restoring from
checkpoints. Unify this by passing the parsed options to the
instantiate() method and adding an optional checkpoint keyword
argument for checkpoint directories (only used by the dist-gem5
script).

Change-Id: I9943ec10bd7a256465e29c8de571142ec3fbaa0e
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Reviewed-by: Sascha Bischoff <sascha.bischoff@arm.com>
Reviewed-by: Gabor Dozsa <gabor.dozsa@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2560
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Weiping Liao <weipingliao@google.com>

arm,config: Add dist-gem5 support to the big.LITTLE(tm) config

This patch extends the example big.LITTLE configuration to enable
dist-gem5 simulations of big.LITTLE systems.

Change-Id: I49c095ab3c737b6a082f7c6f15f514c269217756
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>