drm/amdgpu: add powercontainment module parameter

This patch makes powercontainment feature configurable. Currently, the
powercontainment is not very stable, so add a module parameter to
enable/disable it via user mode.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>