soc: bcm: raspberrypi-power: Release firmware handle on unbind

Use devm_rpi_firmware_get() so as to make sure we release RPi's firmware
interface when unbinding the device.

Signed-off-by: Nicolas Saenz Julienne <[e-mail]>
Reviewed-by: Florian Fainelli <[e-mail]>

drivers/soc/bcm/raspberrypi-power.c

···
 		return -ENODEV;
 	}
 
-	rpi_domains->fw = rpi_firmware_get(fw_np);
+	rpi_domains->fw = devm_rpi_firmware_get(&pdev->dev, fw_np);
 	of_node_put(fw_np);
 	if (!rpi_domains->fw)
 		return -EPROBE_DEFER;