[S390] ccw_bus_type: make it static

Make ccw_bus_type static. ccw_device drivers have to
use ccw_driver_register.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index 334459e..df14c51 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -127,7 +127,7 @@
 	return ret;
 }
 
-struct bus_type ccw_bus_type;
+static struct bus_type ccw_bus_type;
 
 static void io_subchannel_irq(struct subchannel *);
 static int io_subchannel_probe(struct subchannel *);
@@ -1970,7 +1970,7 @@
 	.restore = ccw_device_pm_restore,
 };
 
-struct bus_type ccw_bus_type = {
+static struct bus_type ccw_bus_type = {
 	.name   = "ccw",
 	.match  = ccw_bus_match,
 	.uevent = ccw_uevent,
@@ -2110,5 +2110,4 @@
 EXPORT_SYMBOL(ccw_driver_register);
 EXPORT_SYMBOL(ccw_driver_unregister);
 EXPORT_SYMBOL(get_ccwdev_by_busid);
-EXPORT_SYMBOL(ccw_bus_type);
 EXPORT_SYMBOL_GPL(ccw_device_get_subchannel_id);