tile/defconfigs: Remove CONFIG_IPV6_PRIVACY

Option is long gone, see

  5d9efa7e ("ipv6: Remove privacy config option.")

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>