of/platform: fix of_platform_device_destroy comment

Update the comment to of_platform_device_destroy() to reflect that it no
longer returns a status value.

Fixes: 75f353b6 ("of/platform: Fix of_platform_device_destroy...")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>