drm/amd/powerplay: fix a bug on updating sclk for Fiji

Update sclk smc table rather than mclk smc table for sclk updates.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Eric Huang <JinHuiEric.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>