ipv6: Kill unused ip6_prohibit_entry and ip6_blk_hole_entry declarations.

This patch removes ip6_prohibit_entry and ip6_blk_hole_entry
declarations from include/net/ip6_route.h as they are unused.

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>