HID: hid-asus: reset the backlight brightness level on resume

HID: hid-asus: reset the backlight brightness level on resume

Some devices managed by this driver automatically set brightness to 0
before entering a suspended state and reset it back to a default
brightness level after the resume:
this has the effect of having the kernel report wrong brightness
status after a sleep, and on some devices (like the Asus RC71L) that
brightness is the intensity of LEDs directly facing the user.

Fix the above issue by setting back brightness to the level it had
before entering a sleep state.

Signed-off-by: Denis Benato <benato.denis96@gmail.com>
Signed-off-by: Luke D. Jones <luke@ljones.dev>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>