regulator: rpi-panel: Register with a unique backlight name

There's no reason why 2 Raspberry Pi DSI displays can't be
attached to a Pi Compute Module, so the backlight names need to
be unique.

Use the parent dev_name. It's not as readable, but is unique.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com>
Link: https://lore.kernel.org/r/20220124220129.158891-2-detlev.casanova@collabora.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/rpi-panel-attiny-regulator.c

@@ -181,8 +181,7 @@ static int attiny_i2c_probe(struct i2c_client *i2c,
 
 	props.type = BACKLIGHT_RAW;
 	props.max_brightness = 0xff;
-	bl = devm_backlight_device_register(&i2c->dev,
-					    "7inch-touchscreen-panel-bl",
+	bl = devm_backlight_device_register(&i2c->dev, dev_name(&i2c->dev),
 					    &i2c->dev, regmap, &attiny_bl,
 					    &props);
 	if (IS_ERR(bl))