ipv6: use IS_ENABLED()

#if defined(CONFIG_FOO) || defined(CONFIG_FOO_MODULE)

can be replaced by

#if IS_ENABLED(CONFIG_FOO)

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/xfrm6_state.c b/net/ipv6/xfrm6_state.c
index 3f2f7c4..d8c70b8 100644
--- a/net/ipv6/xfrm6_state.c
+++ b/net/ipv6/xfrm6_state.c
@@ -101,7 +101,7 @@
 			return 1;
 		else
 			return 3;
-#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
+#if IS_ENABLED(CONFIG_IPV6_MIP6)
 	case XFRM_MODE_ROUTEOPTIMIZATION:
 	case XFRM_MODE_IN_TRIGGER:
 		return 2;
@@ -134,7 +134,7 @@
 	switch (v->mode) {
 	case XFRM_MODE_TRANSPORT:
 		return 1;
-#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
+#if IS_ENABLED(CONFIG_IPV6_MIP6)
 	case XFRM_MODE_ROUTEOPTIMIZATION:
 	case XFRM_MODE_IN_TRIGGER:
 		return 2;