Revert "ipv6: ip6_append_data_mtu did not care about pmtudisc and frag_size"

This reverts commit cb607f57c5ff32f8dc3e9efba2a1ed58bd826c41.
Revert "Bluetooth: Fix invalid length check in l2cap_information_rsp()"

This reverts commit d8f6d5b0d276bd0e8a62bf35f682484c4d117163.
15. If empty, please disregard.