config(8): Remove obsolete 'config' directive.

The "config" line in config files has been obsolete since FreeBSD 4.x
when we moved to having the boot loader pass in the root device. Remove
it.

MFC After:		1 week
Sponsored by:		Netflix

usr.sbin/config/config.5

@@ -402,18 +402,6 @@ Options specific to architecture
 are specified in the file
 .Pa sys/conf/options . Ns Aq Ar arch .
 .El
-.Ss Obsolete Directives
-The following kernel configuration directives are obsolete.
-.Bl -tag -width indent
-.\" -------- CONFIG --------
-.It Ic config
-This directive was used to specify the device to be used for the root
-file system.
-From
-.Fx 4.0
-onwards, this information is passed to a booting kernel by
-.Xr loader 8 .
-.El
 .Sh FILES
 .Bl -tag -width ".Pa sys/conf/Makefile. Ns Ar arch" -compact
 .It Pa sys/compile/ Ns Ar NAME

usr.sbin/config/config.y

@@ -203,15 +203,6 @@ Config_spec:
 		STAILQ_INSERT_HEAD(&hints, hint, hint_next);
 	        }
 
-System_spec:
-	CONFIG System_id System_parameter_list {
-		errx(1, "%s:%d: root/dump/swap specifications obsolete",
-		      yyfile, yyline);
-		}
-	  |
-	CONFIG System_id
-	  ;
-
 System_id:
 	Save_id { newopt(&mkopt, ns("KERNEL"), $1, 0, 0); };
 

usr.sbin/config/lang.l

@@ -62,7 +62,6 @@ struct kt {
 	const char *kt_name;
 	int kt_val;
 } key_words[] = {
-	{ "config",	CONFIG },
 	{ "cpu",	CPU },
 	{ "nocpu",	NOCPU },
 	{ "device",	DEVICE },