arch: Detect and convert zero registers to InvalidRegClass.

Change-Id: Ic5e070d303bf05ed1640b441e498d879764b8778
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/49745
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
6 files changed