Currently these kernel packages only work on x86, restrict them to that
target.
Fixes: 2f239c02a031 ("x86: video: add amdgpu DRM kernel package")
Fixes: 2f6918ee9be9 ("x86: video: add radeon DRM module support")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>