ipv4: use IS_ENABLED() instead of checking for built-in or module

The IS_ENABLED() macro checks if a Kconfig symbol has been enabled either
built-in or as a module, use that macro instead of open coding the same.

Using the macro makes the code more readable by helping abstract away some
of the Kconfig built-in and module enable details.
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_output.c

@@ -490,7 +490,7 @@ static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 	to->tc_index = from->tc_index;
 #endif
 	nf_copy(to, from);
-#if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
+#if IS_ENABLED(CONFIG_IP_VS)
 	to->ipvs_property = from->ipvs_property;
 #endif
 	skb_copy_secmark(to, from);