Result of audit to check that mbuf length is checked before m_copydata()
and that any data supposedly copied out is valid before use.

prompted by maxv@, I have checked every usage of m_copydata() and made
the following corrections

hci_event.c:
hci_event_command_compl()
check that the packet does contain enough data for there to
be a status code before noting possible failures.

hci_event_num_compl_pkts()
check that the packet does contain data to cover the
stated number of handle/num pairs

l2cap_signal.c:
l2cap_recv_signal()
just ignore packets with not enough data rather than
trying to reject them (may not have cmd.ident)

l2cap_recv_command_rej()
check we have a valid reason and/or data before use

(plunky)