[SOCK][NETNS]: Add a struct net argument to sock_prot_inuse_add and _get.

This counter is about to become per-proto-and-per-net, so we'll need 
two arguments to determine which cell in this "table" to work with.

All the places, but proc already pass proper net to it - proc will be
tuned a bit later.

Some indentation with spaces in proc files is done to keep the file
coding style consistent.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>