drm/amd/amdgpu: Correct whitespace in SI DPM code

Replace 8 spaces with tabs, correct {} braces, etc.
Signed-off-by: NTom St Denis <tom.stdenis@amd.com>
Reviewed-by: NEdward O'Callaghan <funfunctor@folklore1984.net>
Reviewed-by: NHuang Rui <ray.huang@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>