arch-arm: Introduce update method in ArmFault class

arch-arm: Introduce update method in ArmFault class

There is a set of internal variables in ArmFault thats get updated once
the fault is invoked (ArmFault::invoke). Sometimes we rely on those even
if the fault is generated but not invoked (e.g. when checking if a
memory access is producing a fault). This patch is moving the update
functionalities inside a public method so that a client can make use of
it even when not invoking the fault.

Change-Id: I3ac5b6835023f28ec569fe25487dffa356e1b2fd
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/8361
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>