drm/amd/amdgpu: Clean up memory leak in cz_dpm_init().

If init fails free up any allocated memory.

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>