dev-arm: Add redistributor-stride property to GICv3

dev-arm: Add redistributor-stride property to GICv3

This is needed since by default the model is assuming a GICv4
memory layout.

Change-Id: Ic64e6a488cc1a43a56ce28f6d11b8868df102aa0
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Ciro Santilli <ciro.santilli@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20248
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>