arch-arm: Add a reverse map MiscRegIndex -> MiscRegNum64

Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Change-Id: I63cdcdfca610cfd37a03769e077388a193510bc7
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/55606
Reviewed-by: Richard Cooper <richard.cooper@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
2 files changed