e1000: remove unused and incorrect code

The e1000_clear_vfta function was triggering a warning in kbuild-bot
testing. It's actually a bug but has no functional impact.

drivers/net/ethernet/intel/e1000/e1000_hw.c:4415:58: warning: Same expression in both branches of ternary operator. [duplicateExpressionTernary]

Fix this warning by removing the offending code and simplifying
the routine to do exactly what it did before, no functional
change.
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/intel/e1000/e1000_hw.c

@@ -4401,17 +4401,9 @@ void e1000_write_vfta(struct e1000_hw *hw, u32 offset, u32 value)
 static void e1000_clear_vfta(struct e1000_hw *hw)
 {
 	u32 offset;
-	u32 vfta_value = 0;
-	u32 vfta_offset = 0;
-	u32 vfta_bit_in_reg = 0;
 
 	for (offset = 0; offset < E1000_VLAN_FILTER_TBL_SIZE; offset++) {
-		/* If the offset we want to clear is the same offset of the
-		 * manageability VLAN ID, then clear all bits except that of the
-		 * manageability unit
-		 */
-		vfta_value = (offset == vfta_offset) ? vfta_bit_in_reg : 0;
-		E1000_WRITE_REG_ARRAY(hw, VFTA, offset, vfta_value);
+		E1000_WRITE_REG_ARRAY(hw, VFTA, offset, 0);
 		E1000_WRITE_FLUSH();
 	}
 }