[NETFILTER]: Make sure xt_policy.h is unifdef'ed.

Since the header file xt_policy.h tests __KERNEL__, it should be
unifdef'ed before exporting to userspace.
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter/Kbuild

@@ -30,7 +30,6 @@ header-y += xt_mark.h
 header-y += xt_multiport.h
 header-y += xt_owner.h
 header-y += xt_pkttype.h
-header-y += xt_policy.h
 header-y += xt_rateest.h
 header-y += xt_realm.h
 header-y += xt_sctp.h
@@ -47,3 +46,4 @@ unifdef-y += nfnetlink.h
 unifdef-y += nfnetlink_compat.h
 unifdef-y += x_tables.h
 unifdef-y += xt_physdev.h
+unifdef-y += xt_policy.h