dev-arm: TnSZ fields need to be cached in SMMUv3::ConfigCache

dev-arm: TnSZ fields need to be cached in SMMUv3::ConfigCache

Otherwise a hit after a table walk will result in a 0 value being
read from the ConfigCache.

Change-Id: I9813998acce44c93c5ce203f252ca80c10ba8f38
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Michiel Van Tol <michiel.vantol@arm.com>
Reviewed-by: Adrian Herrera <adrian.herrera@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19631
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>