DCB: fix kconfig option

Since the netlink option for DCB is necessary to actually be useful,
simplified the Kconfig option.  In addition, added useful help text for the
Kconfig option.

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 76a89f8..0df0db0 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -43,7 +43,7 @@
 
 #include <net/net_namespace.h>
 #include <net/dsa.h>
-#ifdef CONFIG_DCBNL
+#ifdef CONFIG_DCB
 #include <net/dcbnl.h>
 #endif
 
@@ -847,7 +847,7 @@
 #define GSO_MAX_SIZE		65536
 	unsigned int		gso_max_size;
 
-#ifdef CONFIG_DCBNL
+#ifdef CONFIG_DCB
 	/* Data Center Bridging netlink ops */
 	struct dcbnl_rtnl_ops *dcbnl_ops;
 #endif