PNPACPI: add bus number support

Add support for bus number resources.  This is for bridges with a range of
bus numbers behind them.  Previously, PNP ignored bus number resources.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/pnp/support.c b/drivers/pnp/support.c
index 9585c1c..f5beb24 100644
--- a/drivers/pnp/support.c
+++ b/drivers/pnp/support.c
@@ -69,8 +69,10 @@
 		return "irq";
 	case IORESOURCE_DMA:
 		return "dma";
+	case IORESOURCE_BUS:
+		return "bus";
 	}
-	return NULL;
+	return "unknown";
 }
 
 void dbg_pnp_show_resources(struct pnp_dev *dev, char *desc)