drm/amdgpu: fix the waring dereferencing hive

Check the amdgpu_hive_info *hive that maybe is NULL.

Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Reviewed-by: Tim Huang <Tim.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>