Input: 88pm860x - use cleanup facility for device_node

Input: 88pm860x - use cleanup facility for device_node

Use the '__free(device_node)' macro to simplify the code and error
handling. This makes the code more robust by ensuring that the device
node is always freed.

Drop the first assignment to 'pdev->dev.parent->of_node', as it was only
a shortcut, and tie 'np' to its usage as a child node.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20241010-input_automate_of_node_put-v1-7-ebc62138fbf8@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>