lantiq: cleanup code ar9-vr9 parts

- remove unused code within 500-ar9_vr9.patch
- fixed return of IFX_ERROR (solves SIGSEGV in asterisk at failure)
- align it a bit with 400-falcon.patch
- remove 600-kernel-4.9.patch since changed parts
  are removed during cleanup

Signed-off-by: Stefan Koch <stefan.koch10@gmail.com>