[NET]: Round out in-kernel sockets API

This patch implements wrapper functions that provide a convenient way
to access the sockets API for in-kernel users like sunrpc, cifs &
ocfs2 etc and any future users.

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: David S. Miller <davem@davemloft.net>