Include "netlink.h" instead of <linux/netlink.h>

Include "netlink.h" instead of <linux/netlink.h>

* net.c: Include "netlink.h" instead of <linux/netlink.h>.
* sockaddr.c: Likewise.
* tests/create_nl_socket.c: Likewise.
* tests/net-sockaddr.c: Likewise.
* tests/netlink_audit.c: Likewise.
* tests/netlink_generic.c: Likewise.
* tests/netlink_inet_diag.c: Likewise.
* tests/netlink_netfilter.c: Likewise.
* tests/netlink_route.c: Likewise.
* tests/netlink_selinux.c: Likewise.
* tests/netlink_xfrm.c: Likewise.
* tests/net-yy-netlink.c: Include "netlink.h" instead
of <linux/netlink.h>, remove fallback definition of NETLINK_SOCK_DIAG.
* tests/netlink_netlink_diag.c: Likewise.
* tests/netlink_protocol.c: Likewise.
* tests/netlink_sock_diag.c: Likewise.
* tests/netlink_unix_diag.c: Likewise.
* tests/nlattr.c: Likewise.