drm/amd: Taint the kernel when enabling overdrive

drm/amd: Taint the kernel when enabling overdrive

Some distributions have been patching amdgpu to enable overdrive by
default which may compromise stability.  Furthermore when bug reports
are brought upstream it's not obvious that the system has been tampered
with.

When overdrive is enabled taint the kernel and leave a critical message
in the logs for users so that it's obvious in a bug report it's been
tampered with.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>