drm/radeon: stop sending invalid UVD destroy msg

commit 641a0059 upstream.

We also need to check the handle.

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