drm/amd/powerplay: enable/disable NB pstate feature for Carrizo.

Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: David Rokhvarg <David.Rokhvarg@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com>