configs: Updated DTB warnings in fs.py for Arm platforms.

configs: Updated DTB warnings in fs.py for Arm platforms.

fs.py warns when an Arm platform is being created without a DTB file,
if the platform does not support the automatic creation of a DTB.

Updated the list of supported platforms with recent additions in order
to remove incorrect and potentially confusing warnings.

Change-Id: I549124a1afbc36e313f614dccab17973582bc3f7
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/30575
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>