drm/amd/powerplay: dpm clk can be set only when performance level is manual

Add condition to make dpm clk can not be set when perfomance level isn't
equal to manual.
Add mutex lock to smu when set dpm clk.

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Kevin Wang <kevin1.wang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>