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/drivers/net/ixgbe/Makefile b/drivers/net/ixgbe/Makefile
index 3228e50..6e7ef76 100644
--- a/drivers/net/ixgbe/Makefile
+++ b/drivers/net/ixgbe/Makefile
@@ -35,4 +35,4 @@
 ixgbe-objs := ixgbe_main.o ixgbe_common.o ixgbe_ethtool.o \
               ixgbe_82598.o ixgbe_phy.o
 
-ixgbe-$(CONFIG_IXGBE_DCBNL) +=  ixgbe_dcb.o ixgbe_dcb_82598.o ixgbe_dcb_nl.o
+ixgbe-$(CONFIG_IXGBE_DCB) +=  ixgbe_dcb.o ixgbe_dcb_82598.o ixgbe_dcb_nl.o