libnvdimm: provide module_nd_driver wrapper

Provide a module_nd_driver() wrapper over simple nd_driver_register()
nd_driver_unregister() combinations in module_init() and module_exit()
respectively.

Note an explicit nd_driver_unregister() had to be implemented as nd
bus drivers did call device_unregister() direcly in the module_exit()
function.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

include/linux/nd.h

@@ -180,6 +180,12 @@ struct nd_region;
 void nvdimm_region_notify(struct nd_region *nd_region, enum nvdimm_event event);
 int __must_check __nd_driver_register(struct nd_device_driver *nd_drv,
 		struct module *module, const char *mod_name);
+static inline void nd_driver_unregister(struct nd_device_driver *drv)
+{
+	driver_unregister(&drv->drv);
+}
 #define nd_driver_register(driver) \
 	__nd_driver_register(driver, THIS_MODULE, KBUILD_MODNAME)
+#define module_nd_driver(driver) \
+	module_driver(driver, nd_driver_register, nd_driver_unregister)
 #endif /* __LINUX_ND_H__ */