greybus: connection: drop unneeded gb_protocol_put() calls

Although a connection records its protocol id when it gets
created, its protocol handler doesn't actually get assigned
until gb_connection_bind_protocol() is called.

In gb_connection_create() there are some error paths in
which a reference to the connection's protocol is released
before the protocol handler has been associated with the
connection.

Get rid of those calls.

As a result, we will never pass a null protocol pointer to
gb_protocol_put().  Add a precautionary warning in that
function in the event that ever occurs.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/connection.c

@@ -195,7 +195,6 @@ struct gb_connection *gb_connection_create(struct gb_bundle *bundle,
 	connection->major = major;
 	connection->minor = minor;
 	if (!gb_connection_hd_cport_id_alloc(connection)) {
-		gb_protocol_put(connection->protocol);
 		kfree(connection);
 		return NULL;
 	}
@@ -217,7 +216,6 @@ struct gb_connection *gb_connection_create(struct gb_bundle *bundle,
 		pr_err("failed to add connection device for cport 0x%04hx\n",
 			cport_id);
 		gb_connection_hd_cport_id_free(connection);
-		gb_protocol_put(connection->protocol);
 		put_device(&connection->dev);
 
 		return NULL;
@@ -264,6 +262,7 @@ void gb_connection_destroy(struct gb_connection *connection)
 
 	gb_connection_hd_cport_id_free(connection);
 	gb_protocol_put(connection->protocol);
+	connection->protocol = NULL;
 
 	device_unregister(&connection->dev);
 }

drivers/staging/greybus/protocol.c

@@ -196,7 +196,7 @@ void gb_protocol_put(struct gb_protocol *protocol)
 	u8 minor;
 	u8 protocol_count;
 
-	if (!protocol)
+	if (WARN_ON(!protocol))
 		return;
 
 	id = protocol->id;