e1000: 3 new driver stats for managability testing

Add 3 extra packet redirect counters for tracking purposes to make sure
we can test that all packets arrive properly.

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_ethtool.c b/drivers/net/e1000/e1000_ethtool.c
index da459f7..fb96c87 100644
--- a/drivers/net/e1000/e1000_ethtool.c
+++ b/drivers/net/e1000/e1000_ethtool.c
@@ -100,6 +100,9 @@
 	{ "rx_csum_offload_errors", E1000_STAT(hw_csum_err) },
 	{ "rx_header_split", E1000_STAT(rx_hdr_split) },
 	{ "alloc_rx_buff_failed", E1000_STAT(alloc_rx_buff_failed) },
+	{ "tx_smbus", E1000_STAT(stats.mgptc) },
+	{ "rx_smbus", E1000_STAT(stats.mgprc) },
+	{ "dropped_smbus", E1000_STAT(stats.mgpdc) },
 };
 
 #define E1000_QUEUE_STATS_LEN 0