style: fix amd license and style issues

Change-Id: I26136fb49f743c4a597f8021cfd27f78897267b5
Reviewed-on: https://gem5-review.googlesource.com/10463
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>

misc: Add missing overrides to appease clang

Since the last round of fixes a few new issues have snuck in. We
should consider switching the regression runs to clang.

gpu-compute: AMD's baseline GPU model