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/xfrm4_state.c b/net/ipv4/xfrm4_state.c
index d9ac0a0..9258e75 100644
--- a/net/ipv4/xfrm4_state.c
+++ b/net/ipv4/xfrm4_state.c
@@ -12,6 +12,7 @@
 #include <linux/pfkeyv2.h>
 #include <linux/ipsec.h>
 #include <linux/netfilter_ipv4.h>
+#include <linux/export.h>
 
 static int xfrm4_init_flags(struct xfrm_state *x)
 {