This implements sclk overdrive(OD) overclocking support for Tonga,
and the maximum overdrive percentage is 20.
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NEric Huang <JinHuiEric.Huang@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>