[IPV4]: inetpeer annotations

This one is interesting - we use net-endian value as search key, but
order the tree by *host-endian* comparisons of keys.  OK since we only
care about lookups.  Annotated inet_getpeer() and friends.

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