leds: leds-88pm860x: drop devm_kfree of devm_kzalloc'd data

The devm_kfree function allocates memory that is released
when a driver detaches. Thus, there is no reason to explicitly
call devm_kfree in probe or remove functions.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>