drm/amd/amdgpu: fix the GPU power print error in pm info

Modify the print format of the fractional part to avoid display error.

Signed-off-by: Li Ma <li.ma@amd.com>
Reviewed-by: Yifan Zhang <yifan1.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>