mesa: refuse to change tex buffers when a handle is allocated

mesa: refuse to change tex buffers when a handle is allocated

The ARB_bindless_texture spec says:

   "The error INVALID_OPERATION is generated by BufferData if it is
    called to modify a buffer object bound to a buffer texture while
    that texture object is referenced by one or more texture handles."

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>