net: Add export.h for EXPORT_SYMBOL/THIS_MODULE to non-modules

These files are non modular, but need to export symbols using
the macros now living in export.h -- call out the include so
that things won't break when we remove the implicit presence
of module.h from everywhere.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index 472a8c4..0da2afc 100644
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -54,6 +54,7 @@
 #include <linux/delay.h>
 #include <linux/nfs_fs.h>
 #include <linux/slab.h>
+#include <linux/export.h>
 #include <net/net_namespace.h>
 #include <net/arp.h>
 #include <net/ip.h>