xfrm: add UDP encapsulation port in migrate message

Add XFRMA_ENCAP, UDP encapsulation port, to km_migrate announcement
to userland. Only add if XFRMA_ENCAP was in user migrate request.

Signed-off-by: Antony Antony <antony@phenome.org>
Reviewed-by: Richard Guy Briggs <rgb@tricolour.ca>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index d47f055..e614189 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -3384,7 +3384,7 @@ int xfrm_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 	}
 
 	/* Stage 5 - announce */
-	km_migrate(sel, dir, type, m, num_migrate, k);
+	km_migrate(sel, dir, type, m, num_migrate, k, encap);
 
 	xfrm_pol_put(pol);