drivers: make device_type const

The device_type structure does not contain data that changes
during usage and should be const. This allows devices to declare
the struct const.

I have patches to change all the subsystems, but need the infra
structure change first.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 81b78ed..fb8130c 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -400,7 +400,7 @@
 static int device_add_attrs(struct device *dev)
 {
 	struct class *class = dev->class;
-	struct device_type *type = dev->type;
+	const struct device_type *type = dev->type;
 	int error;
 
 	if (class) {
@@ -440,7 +440,7 @@
 static void device_remove_attrs(struct device *dev)
 {
 	struct class *class = dev->class;
-	struct device_type *type = dev->type;
+	const struct device_type *type = dev->type;
 
 	device_remove_groups(dev, dev->groups);