gpio: label descriptors using the device name

Some GPIO lines appear named "?" in the lsgpio dump due to their
requesting drivers not passing a reasonable label.

Most typically this happens if a device tree node just defines
gpios = <...> and not foo-gpios = <...>, the former gets named
"foo" and the latter gets named "?".

However the struct device passed in is always valid so let's
just label the GPIO with dev_name() on the device if no proper
label was passed.

Cc: Reported-by: Jason Kridner <jkridner@beagleboard.org>
Reported-by: Jason Kridner <jkridner@beagleboard.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -3650,7 +3650,8 @@ struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
 		return desc;
 	}
 
-	status = gpiod_request(desc, con_id);
+	/* If a connection label was passed use that, else use the device name as label */
+	status = gpiod_request(desc, con_id ? con_id : dev_name(dev));
 	if (status < 0)
 		return ERR_PTR(status);