drm/amd/pm: fix pp_dpm_sclk node not displaying correctly

if GFX clock is in DS (Deep Sleep) state, the current gfx freq may less then dpm
level 0, then pp_dpm_sclk node unable show correct freq.

(align output format with other cards)

Signed-off-by: Yang Wang <kevinyang.wang@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>