leds: 88pm860x: fix use-after-free on unbind

leds: 88pm860x: fix use-after-free on unbind

commit eca21c2d8655387823d695b26e6fe78cf3975c05 upstream.

Several MFD child drivers register their class devices directly under
the parent device. This means you cannot blindly do devres conversions
so that deregistration ends up being tied to the parent device,
something which leads to use-after-free on driver unbind when the class
device is released while still being registered.

Fixes: 375446df95ee ("leds: 88pm860x: Use devm_led_classdev_register")
Cc: stable <stable@vger.kernel.org>     # 4.6
Cc: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>