Standardised debug messages to make it easy to get a bus scan printout

(just build debugging versions of the relevant bus objects).

src/drivers/bus/eisa.c

 	eisa->prod_id = ( inb ( eisa->ioaddr + EISA_PROD_ID_LO ) << 8 )
 		+ inb ( eisa->ioaddr + EISA_PROD_ID_HI );
 
-	DBG ( "EISA slot %d (base %#hx) ID %hx:%hx (\"%s\")\n",
+	DBG ( "EISA found slot %d (base %#hx) ID %hx:%hx (\"%s\")\n",
 	      eisa->slot, eisa->ioaddr, eisa->mfg_id, eisa->prod_id,
 	      isa_id_string ( eisa->mfg_id, eisa->prod_id ) );
 

src/drivers/bus/mca.c

 	/* Kill all setup modes */
 	outb_p ( 0, MCA_ADAPTER_SETUP_REG );
 
-	DBG ( "MCA slot %d id %hx (%hhx:%hhx:%hhx:%hhx:%hhx:%hhx:%hhx:%hhx)\n",
+	DBG ( "MCA found slot %d id %hx "
+	      "(POS %hhx:%hhx:%hhx:%hhx:%hhx:%hhx:%hhx:%hhx)\n",
 	      mca->slot, MCA_ID ( mca ),
 	      mca->pos[0], mca->pos[1], mca->pos[2], mca->pos[3],
 	      mca->pos[4], mca->pos[5], mca->pos[6], mca->pos[7] );

src/drivers/bus/pci.c

 		pci_read_config_byte ( pci, PCI_INTERRUPT_LINE, &pci->irq );
 	}
 
-	DBG ( "%hhx:%hhx.%d Class %hx: %hx:%hx (rev %hhx)\n",
+	DBG ( "PCI found %hhx:%hhx.%d Class %hx: %hx:%hx (rev %hhx)\n",
 	      PCI_BUS ( pci->busdevfn ), PCI_DEV ( pci->busdevfn ),
 	      PCI_FUNC ( pci->busdevfn ), pci->class, pci->vendor, pci->dev_id,
 	      pci->revision );

src/drivers/net/3c509.c

 			DBG ( "No ID port available for contention select\n" );
 			return 0;
 		}
+		DBG ( "T509 scan using ID port at %hx\n", t509->id_port );
 	}
 
 	/* 
 	outb ( ++t509->current_tag, t509->id_port ); /* tag */
 	outb ( ( 0xe0 | iobase ), t509->id_port ); /* activate */
 
+	DBG ( "T509 found at %hx (tagged as %hhx)\n", t509->ioaddr,
+	      t509->current_tag );
+
 	return 1;
 }