arch-arm: Implement Armv8.2-LPA

arch-arm: Implement Armv8.2-LPA

This is enabled by setting the ArmSystem.phys_addr_range64 to 52.
This will automatically set the ID_AA64MMFR0_EL1.PARange to 0b0110
which encodes the presence of Armv8.2-LPA

Change-Id: If9b36e26cd2a72e55c8e929a632b7b50d909b282
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/35956
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>