ixgbe: define IXGBE_MAX_VFS_DRV_LIMIT macro and cleanup const 63

Because ixgbe driver limit the max number of VF
 functions could be enabled to 63, so define one macro IXGBE_MAX_VFS_DRV_LIMIT
 and cleanup the const 63 in code.

v3: revised for net-next tree.

Signed-off-by: Ethan Zhao <ethan.kernel@gmail.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.h b/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.h
index 4713f9f..8bd2919 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.h
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.h
@@ -28,6 +28,11 @@
 #ifndef _IXGBE_SRIOV_H_
 #define _IXGBE_SRIOV_H_
 
+/*  ixgbe driver limit the max number of VFs could be enabled to
+ *  63 (IXGBE_MAX_VF_FUNCTIONS - 1)
+ */
+#define IXGBE_MAX_VFS_DRV_LIMIT  (IXGBE_MAX_VF_FUNCTIONS - 1)
+
 void ixgbe_restore_vf_multicasts(struct ixgbe_adapter *adapter);
 void ixgbe_msg_task(struct ixgbe_adapter *adapter);
 int ixgbe_vf_configuration(struct pci_dev *pdev, unsigned int event_mask);