make pnp.h self contained, for what good it'll do since it's days are

numbered (new pnp-aware isa code in the pipeline).

sys/i386/isa/pnp.h

@@ -29,7 +29,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *      $Id: pnp.h,v 1.6 1998/01/10 07:41:43 kato Exp $
+ *      $Id: pnp.h,v 1.7 1998/09/13 22:15:44 eivind Exp $
  */
 
 #ifndef _I386_ISA_PNP_H_
@@ -267,6 +267,8 @@ struct pnp_cinfo {
 
 #ifdef KERNEL
 
+struct isa_device;
+
 struct pnp_device {
     char *pd_name;
     char * (*pd_probe ) (u_long csn, u_long vendor_id);