ixgb(4): Add deprecation notice for this old and busted 10GE adapter.

This is a prequisite before we remove the driver from -current.

Reviewed by:	emaste kbowling imp
Relnotes:	yes
Differential Revision:	https://reviews.freebsd.org/D15244

share/man/man4/ixgb.4

@@ -31,7 +31,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd August 18, 2006
+.Dd April 30, 2018
 .Dt IXGB 4
 .Os
 .Sh NAME
@@ -51,6 +51,12 @@ module at boot time, place the following line in
 .Bd -literal -offset indent
 if_ixgb_load="YES"
 .Ed
+.Sh DEPRECATION NOTICE
+The
+.Nm
+driver is not present in
+.Fx 12.0
+and later.
 .Sh DESCRIPTION
 The
 .Nm

sys/dev/ixgb/if_ixgb.c

@@ -350,6 +350,7 @@ ixgb_attach(device_t dev)
 	ixgb_clear_hw_cntrs(&adapter->hw);
 	ixgb_update_stats_counters(adapter);
 
+	gone_in_dev(dev, 12, "ixgb(4) driver");
 	INIT_DEBUGOUT("ixgb_attach: end");
 	return (0);