drm/nouveau: Adding support to control backlight using bl_power for nva3.
Test plan:
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Turn off: echo 1 > /sys/class/backlight/nv_backlight/bl_power
-
Turn on: echo 0 > /sys/class/backlight/nv_backlight/bl_power
Signed-off-by: antoniospg antoniospg100@gmail.com