net: fib: drop include of module.h from fib_notifier.h

Ideally, header files under include/linux shouldn't be adding
includes of other headers, in anticipation of their consumers,
but just the headers needed for the header itself to pass
parsing with CPP.

The module.h is particularly bad in this sense, as it itself does
include a whole bunch of other headers, due to the complexity of
module support.

Since fib_notifier.h is not going into a module struct looking for
specific fields, we can just let it know that module is a struct,
just like about 60 other include/linux headers already do.

Cc: "David S. Miller" <[e-mail]>
Signed-off-by: Paul Gortmaker <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/fib_notifier.h

···
 #define __NET_FIB_NOTIFIER_H
 
 #include <linux/types.h>
-#include <linux/module.h>
 #include <linux/notifier.h>
 #include <net/net_namespace.h>
+
+struct module;
 
 struct fib_notifier_info {
 	struct net *net;