net: fix build warnings because of net_get_random_once merge

This patch fixes the following warning:

   In file included from include/linux/skbuff.h:27:0,
                    from include/linux/netfilter.h:5,
                    from include/net/netns/netfilter.h:5,
                    from include/net/net_namespace.h:20,
                    from include/linux/init_task.h:14,
                    from init/init_task.c:1:
include/linux/net.h:243:14: warning: 'struct static_key' declared inside parameter list [enabled by default]
          struct static_key *done_key);

on x86_64 allnoconfig, um defconfig and ia64 allmodconfig and maybe others as well.
Signed-off-by: NHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/net.h

@@ -24,6 +24,7 @@
 #include <linux/fcntl.h>	/* For O_CLOEXEC and O_NONBLOCK */
 #include <linux/kmemcheck.h>
 #include <linux/rcupdate.h>
+#include <linux/jump_label.h>
 #include <uapi/linux/net.h>
 
 struct poll_table_struct;