e1000e: 82574/82583 Tx hang workaround

On 82574/82583, there is a hardware bug which might cause a Tx hang when
the internal buffer is full.  Setting this bit enables a hardware fix to
work around the issue.
Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/e1000e/82571.c

@@ -1227,6 +1227,10 @@ static void e1000_initialize_hw_bits_82571(struct e1000_hw *hw)
 	case e1000_82572:
 		reg |= (1 << 23) | (1 << 24) | (1 << 25) | (1 << 26);
 		break;
+	case e1000_82574:
+	case e1000_82583:
+		reg |= (1 << 26);
+		break;
 	default:
 		break;
 	}