leds: leds-fsg: Use devm_led_classdev_register

Use resource-managed function devm_led_classdev_register instead
of led_classdev_register to make the error-path simpler.

To be compatible with the change, various gotos are replaced with
direct returns and unneeded labels are dropped. Also, remove
fsg_led_remove as it is now redundant.

Signed-off-by: Vaishali Thakkar <vthakkar1994@gmail.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>