ixgbe: Disable DCB and FCoE for X550EM_x and x550em_a

This patch adds IXGBE_FLAG_DCB_CAPABLE flag that is set
for all MACs other than X550EM_x and x550em_a. DCB and
FCoE is disabled for these MACS. DCB initialization
code is moved to a separate function.

Signed-off-by: Usha Ketineni <usha.k.ketineni@intel.com>
Tested-by: Ronald Bynoe <ronald.j.bynoe@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
index e216a3d..9f2db18 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
@@ -644,6 +644,7 @@
 #define IXGBE_FLAG_VXLAN_OFFLOAD_CAPABLE	BIT(24)
 #define IXGBE_FLAG_RX_HWTSTAMP_ENABLED		BIT(25)
 #define IXGBE_FLAG_RX_HWTSTAMP_IN_REGISTER	BIT(26)
+#define IXGBE_FLAG_DCB_CAPABLE			BIT(27)
 
 	u32 flags2;
 #define IXGBE_FLAG2_RSC_CAPABLE			BIT(0)