net: sctp: minor: make sctp_ep_common's member 'dead' a bool

Since dead only holds two states (0,1), make it a bool instead
of a 'char', which is more appropriate for its purpose.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>