e1000e: avoid polling h/w registers during link negotiation

Avoid touching hardware registers when possible, otherwise link negotiation
can get messed up when user-level scripts are rapidly polling the driver to
see if/when link is up.  Use the saved link state information instead when
possible.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@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/netdev.c b/drivers/net/e1000e/netdev.c
index 8faf224..2a71889 100644
--- a/drivers/net/e1000e/netdev.c
+++ b/drivers/net/e1000e/netdev.c
@@ -3964,7 +3964,7 @@
 	       ((ctrl & E1000_CTRL_TFCE) ? "TX" : "None" )));
 }
 
-bool e1000e_has_link(struct e1000_adapter *adapter)
+static bool e1000e_has_link(struct e1000_adapter *adapter)
 {
 	struct e1000_hw *hw = &adapter->hw;
 	bool link_active = 0;