arch-arm: Do not check MustBeOne flag for TLB requests from the prefetcher

arch-arm: Do not check MustBeOne flag for TLB requests from the prefetcher

Allow TLB requests generated from prefetchers to override the
MustBeOne arch flag. This allows the prefetchers to issue requests
without having to know architecutre-specific flags.

Change-Id: Id83e0c93f3d1a614da11c4f344ab4dc594423672
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18768
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>