netfilter: nf_tables: fix implicit include of module.h

This file clearly uses modular infrastructure but does not call
out the inclusion of <linux/module.h> explicitly.  We add that
include explicitly here, so we can tidy up some header usage
elsewhere w/o causing build breakage.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_set_core.c

 /* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/module.h>
 #include <net/netfilter/nf_tables_core.h>
 
 static int __init nf_tables_set_module_init(void)