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>

drivers/net/e1000/e1000_hw.h

@@ -1463,6 +1463,7 @@ struct e1000_hw {
 	boolean_t		kmrn_lock_loss_workaround_disabled;
 	boolean_t		bad_tx_carr_stats_fd;
 	boolean_t		has_manc2h;
+	boolean_t		rx_needs_kicking;
 };