sundance: 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: NJavier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/dlink/sundance.c

@@ -867,7 +867,7 @@ static int netdev_open(struct net_device *dev)
 
 	/* Initialize other registers. */
 	__set_mac_addr(dev);
-#if defined(CONFIG_VLAN_8021Q) || defined(CONFIG_VLAN_8021Q_MODULE)
+#if IS_ENABLED(CONFIG_VLAN_8021Q)
 	iowrite16(dev->mtu + 18, ioaddr + MaxFrameSize);
 #else
 	iowrite16(dev->mtu + 14, ioaddr + MaxFrameSize);