Unify error handling and create factory methods for address generators. Change-Id: Ic3ab705e1bb58affd498a7db176536ebc721b904 Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-on: https://gem5-review.googlesource.com/11516 Reviewed-by: Jason Lowe-Power <jason@lowepower.com>