net: use common macro for assering skb->cb[] available size in protocol families

As part of an effort to move skb->dropcount to skb->cb[] use a common
macro in protocol families using skb->cb[] for ancillary data to
validate available room in skb->cb[].

Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/net/sock.h
Simple merge

diff --cc net/bluetooth/af_bluetooth.c
Simple merge

diff --cc net/can/bcm.c
Simple merge

diff --cc net/can/raw.c
Simple merge

diff --cc net/ipv4/af_inet.c
Simple merge

diff --cc net/ipv4/tcp.c
Simple merge

diff --cc net/ipv6/af_inet6.c
Simple merge

diff --cc net/packet/af_packet.c
Simple merge

diff --cc net/sctp/protocol.c
Simple merge