e1000: workaround for the ESB2 NIC RX unit issue

In rare occasions, ESB2 systems would end up started without the RX
unit being turned on. Add a check that runs post-init to work around
this issue.

Originally from Jesse Brandeburg <jesse.brandeburg@intel.com>,
rewritten to use feature flags by me.

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index 9c24949..343eb68 100644
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -2579,6 +2579,13 @@
 			netif_wake_queue(netdev);
 			mod_timer(&adapter->phy_info_timer, jiffies + 2 * HZ);
 			adapter->smartspeed = 0;
+		} else {
+			/* make sure the receive unit is started */
+			if (adapter->hw.rx_needs_kicking) {
+				struct e1000_hw *hw = &adapter->hw;
+				uint32_t rctl = E1000_READ_REG(hw, RCTL);
+				E1000_WRITE_REG(hw, RCTL, rctl | E1000_RCTL_EN);
+			}
 		}
 	} else {
 		if (netif_carrier_ok(netdev)) {