northbridge: DEVICE_NOOP some stub function callbacks

Reduces loc and makes NOP's explicit.

Change-Id: I8a117b150b8b421c7a18b48a2ac36d15679f20b0
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7344
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/northbridge/amd/agesa/family15tn/northbridge.c b/src/northbridge/amd/agesa/family15tn/northbridge.c
index d77897d..2632321 100644
--- a/src/northbridge/amd/agesa/family15tn/northbridge.c
+++ b/src/northbridge/amd/agesa/family15tn/northbridge.c
@@ -1054,17 +1054,9 @@
 	initialize_cpus(dev->link_list);
 }
 
-static void cpu_bus_read_resources(device_t dev)
-{
-}
-
-static void cpu_bus_set_resources(device_t dev)
-{
-}
-
 static struct device_operations cpu_bus_ops = {
-	.read_resources	  = cpu_bus_read_resources,
-	.set_resources	  = cpu_bus_set_resources,
+	.read_resources	  = DEVICE_NOOP,
+	.set_resources	  = DEVICE_NOOP,
 	.enable_resources = DEVICE_NOOP,
 	.init		  = cpu_bus_init,
 	.scan_bus	  = cpu_bus_scan,