greybus: gpbridge: Export few routines

In order to separate protocol specific drivers into their own modules,
some of the gpbridge routines need to be exported.

Tested on EVT 1.5 by inserting GP test module, all the devices were
enumerated correctly.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/gpbridge.c

@@ -163,11 +163,13 @@ int gb_gpbridge_register_driver(struct gpbridge_driver *driver,
 	pr_info("registered new driver %s\n", driver->name);
 	return 0;
 }
+EXPORT_SYMBOL_GPL(gb_gpbridge_register_driver);
 
 void gb_gpbridge_deregister_driver(struct gpbridge_driver *driver)
 {
 	driver_unregister(&driver->driver);
 }
+EXPORT_SYMBOL_GPL(gb_gpbridge_deregister_driver);
 
 int gb_gpbridge_get_version(struct gb_connection *connection)
 {
@@ -194,6 +196,7 @@ int gb_gpbridge_get_version(struct gb_connection *connection)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(gb_gpbridge_get_version);
 
 static struct gpbridge_device *gb_gpbridge_create_dev(struct gb_bundle *bundle,
 				struct greybus_descriptor_cport *cport_desc)