arch: Re-add copyrights that were accidentally removed.

arch: Re-add copyrights that were accidentally removed.

The partial contents of some files were moved into other files, but the
copyright wasn't moved over with them. This propogates the copyright.

Change-Id: I8612e88ffb7584b15924cf747f671ca3cdefbe55
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/36716
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>