Forcing clock level is supported under manual dpm mode only. Error out
when trying to set under manual mode. Instead of doing nothing and
reporting success.

V2: update for mclk/pcie clock level settings also
Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>