ixgb: add tx timeout counter

This adds a TX timeout counter to the ethtool stats, a tx timeout
debug message, and sets the timer to 5 seconds.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: John Ronciak <john.ronciak@intel.com>

diff --git a/drivers/net/ixgb/ixgb.h b/drivers/net/ixgb/ixgb.h
index a687f12..b9c37fd 100644
--- a/drivers/net/ixgb/ixgb.h
+++ b/drivers/net/ixgb/ixgb.h
@@ -180,6 +180,7 @@
 	uint64_t hw_csum_tx_good;
 	uint64_t hw_csum_tx_error;
 	uint32_t tx_int_delay;
+	uint32_t tx_timeout_count;
 	boolean_t tx_int_delay_enable;
 	boolean_t detect_tx_hung;