When two VMs stop using PRT support at the same time we might
not disable it in the right order otherwise.

v2: agd: rebase
Signed-off-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NNicolai Hähnle <nicolai.haehnle@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>