Avoid calling thunderstrike_led_set_brightness from thunderstrike_create
when led_classdev_unregister is called. led_classdev_unregister was called
from thunderstrike_create in the error path. Calling
thunderstrike_led_set_brightness in this situation is unsafe.

Fixes: f88af60e ("HID: nvidia-shield: Support LED functionality for Thunderstrike")
Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>