Add deprecation notice for lmc(4)

We intend to remove support before FreeBSD 12 is branched.  These are
available only as 32-bit PCI devices.  The driver has an ambiguous
license and I have not been successful in contacting the driver's author
in order to address this.

The planned deprecation has been announced on -current and -stable; if
we receive feedback that the driver is still useful and we are able to
resolve the license issue this deprecation notice can be reverted.

Reviewed by:	bapt, brooks, imp, rgrimes
MFC after:	2 weeks
Relnotes:	Yes
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D15182

share/man/man4/lmc.4

@@ -43,7 +43,7 @@
 .\" this program; if not, write to the Free Software Foundation, Inc., 59
 .\" Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 .\"
-.Dd February 8, 2012
+.Dd April 24, 2018
 .Dt LMC 4
 .Os
 .\"
@@ -89,6 +89,13 @@ Netgraph and SPPP can both be enabled; Netgraph will be used if the
 .Va rawdata
 hook is connected.
 .\"
+.Sh DEPRECATION NOTICE
+The
+.Nm
+driver is not present in
+.Fx 12.0
+and later.
+.\"
 .Sh DESCRIPTION
 .\"
 This is an open-source

sys/dev/lmc/if_lmc.c

@@ -4547,6 +4547,7 @@ fbsd_attach(device_t dev)
 
   /* Start the card and attach a kernel interface and line protocol. */
   if ((error = attach_card(sc, ""))) detach_card(sc);
+  gone_in_dev(dev, 12, "lmc(4) driver");
   return error;
   }