Enable/disable the handling globally for now and
print a warning when we enable it for the first time.

v2: set correct register
Signed-off-by: NJunwei Zhang <Jerry.Zhang@amd.com>
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>