igb: fix unused external references introduced with sr-iov changes

There were several unused external references added with the sr-iov
enablement changes.  This patch changes all those references to static
local references.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/igb/e1000_mac.c

@@ -111,7 +111,7 @@ void igb_clear_vfta(struct e1000_hw *hw)
  *  Writes value at the given offset in the register array which stores
  *  the VLAN filter table.
  **/
-void igb_write_vfta(struct e1000_hw *hw, u32 offset, u32 value)
+static void igb_write_vfta(struct e1000_hw *hw, u32 offset, u32 value)
 {
 	array_wr32(E1000_VFTA, offset, value);
 	wrfl();