net: Kill hold_net release_net

hold_net and release_net were an idea that turned out to be useless.
The code has been disabled since 2008.  Kill the code it is long past due.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/linux/netdevice.h
Simple merge

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

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

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

diff --cc net/core/dev.c
Simple merge

diff --cc net/core/fib_rules.c
Simple merge

diff --cc net/core/neighbour.c
Simple merge

diff --cc net/core/net_namespace.c
Simple merge

diff --cc net/core/sock.c
Simple merge

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

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

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

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

diff --cc net/ipv6/ip6_flowlabel.c
Simple merge

diff --cc net/openvswitch/datapath.c
Simple merge