greybus: protocol: Add gb_gpbridge_protocol_driver()

There are many gpbridge protocol drivers that need gb_protocol_driver()
without the module_init/exit() lines. Lets create one for them.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/protocol.h

@@ -90,6 +90,7 @@ extern void gb_hid_protocol_exit(void);
 extern int gb_audio_protocol_init(void);
 extern void gb_audio_protocol_exit(void);
 
+/* __protocol: Pointer to struct gb_protocol */
 #define gb_protocol_driver(__protocol)			\
 static int __init protocol_init(void)			\
 {							\
@@ -102,6 +103,17 @@ static void __exit protocol_exit(void)			\
 }							\
 module_exit(protocol_exit)
 
+/* __protocol: string matching name of struct gb_protocol */
+#define gb_gpbridge_protocol_driver(__protocol)		\
+int __init gb_##__protocol##_init(void)			\
+{							\
+	return gb_protocol_register(&__protocol);	\
+}							\
+void __exit gb_##__protocol##_exit(void)		\
+{							\
+	gb_protocol_deregister(&__protocol);		\
+}							\
+
 /*
  * Macro to create get_version() routine for protocols
  * @__device: name of the device struct