Add linux/net.h to the list of headers for libconstants

This change adds linux/net.h so that those socket function constants,
SYS_*, for socketcall(2) are available in seccomp policy files.

Bug: None
Test: make && grep SYS_ libconstants.gen.c
Change-Id: I85568c229f23570e889cd938ea53ee1566e7bbe1
diff --git a/gen_constants-inl.h b/gen_constants-inl.h
index 752badc..7d9f915 100644
--- a/gen_constants-inl.h
+++ b/gen_constants-inl.h
@@ -5,6 +5,7 @@
 #include <fcntl.h>
 #include <linux/fs.h>
 #include <linux/mman.h>
+#include <linux/net.h>
 #include <linux/prctl.h>
 #include <linux/sched.h>
 #include <linux/serial.h>