radv: Remove syncobj_handle variable in header.

radv: Remove syncobj_handle variable in header.

I strongly suspect it was supposed to be a typedef. However, used
nowhere, we should remove it.

Fixes: eaa56eab6da "radv: initial support for shared semaphores (v2)"
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2385
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3479>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3479>