[SCTP]: Switch ->cmp_addr() and sctp_cmp_addr_exact() to net-endian.

instances of ->cmp_addr() are fine with switching both arguments
to net-endian; callers other than in sctp_cmp_addr_exact() (both
as ->cmp_addr(...) and direct calls of instances) adjusted;
sctp_cmp_addr_exact() switched to net-endian itself and adjustment
is done in its callers

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>