drm/amdgpu: fix error handling in amdgpu_bo_do_create

commit a695e43712242c354748e9bae5d137d4337a7694 upstream.

The bo structure is freed up in case of an error, so we can't do any
accounting if that happens.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>