e1000e: PHY loopback broken on 82578

PHY loopback on 82578 fails to work as a result of flushing the packets
in the FIFO buffer in the link stall workaround.  Don't perform the
workaround if in PHY loopback mode.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/e1000e/defines.h b/drivers/net/e1000e/defines.h
index 8890c97..4329ec3 100644
--- a/drivers/net/e1000e/defines.h
+++ b/drivers/net/e1000e/defines.h
@@ -575,6 +575,8 @@
 #define PHY_1000T_STATUS 0x0A /* 1000Base-T Status Reg */
 #define PHY_EXT_STATUS   0x0F /* Extended Status Reg */
 
+#define PHY_CONTROL_LB   0x4000 /* PHY Loopback bit */
+
 /* NVM Control */
 #define E1000_EECD_SK        0x00000001 /* NVM Clock */
 #define E1000_EECD_CS        0x00000002 /* NVM Chip Select */