leds: max8997: Use devm_led_classdev_register

Switch to resource-managed function devm_led_classdev_register instead
of led_classdev_register and remove unneeded led_classdev_unregister.

Also, remove platform_set_drvdata in probe function and the remove
function, max8997_led_remove as it is now has nothing to do.

The Coccinelle semantic patch used to make this change is as follows:
//<smpl>
@platform@
identifier p, probefn, removefn;
@@
struct platform_driver p = {
  .probe = probefn,
  .remove = removefn,
};

@prb@
identifier platform.probefn, pdev;
expression e;
@@
probefn(struct platform_device *pdev, ...) {
  ...
  e =
- led_classdev_register
+ devm_led_classdev_register
  (...);
   ...
?- led_classdev_unregister(...);
  ...
}
@remove depends on prb@
identifier platform.removefn;
@@
removefn(...) {
...
?- led_classdev_unregister(...);
...
}
//</smpl>

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>