Don't panic when we're asked to allocate a resource type that we know

won't exist for EBus. Just fail the allocation by returning NULL.
Now drivers that are MI can try resources that the driver knows may
be used by the device.

sys/sparc64/ebus/ebus.c

@@ -353,10 +353,9 @@ ebus_alloc_resource(device_t bus, device_t child, int type, int *rid,
 	case SYS_RES_IRQ:
 		return (resource_list_alloc(rl, bus, child, type, rid, start,
 		    end, count, flags));
-	default:
-		panic("ebus_alloc_resource: unsupported resource type %d",
-		    type);
 	}
+
+	return (NULL);
 }
 
 int