amdgpu/pm: Implement emit_clk_levels for vega10

   (v1)
     - implement emit_clk_levels for vega10, based on print_clk_levels,
       but using sysfs_emit rather than sprintf
     - modify local int vars to use uint32_t to match arg type of
       called functions
     - add return of error codes
     - refactor OD_XXX cases to return early with -EOPNOTSUPP if
       !(hwmgr->od_enabled)

Signed-off-by: Darren Powell <darren.powell@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>