remove "struct subsystem" as it is no longer needed

We need to work on cleaning up the relationship between kobjects, ksets and
ktypes.  The removal of 'struct subsystem' is the first step of this,
especially as it is not really needed at all.

Thanks to Kay for fixing the bugs in this patch.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/base/base.h b/drivers/base/base.h
index d597f26..5512d84 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -45,3 +45,5 @@
 extern char *make_class_name(const char *name, struct kobject *kobj);
 
 extern void devres_release_all(struct device *dev);
+
+extern struct kset devices_subsys;