ACPI: video: Add backlight=native DMI quirk for Dell G15 5515

The Dell G15 5515 has the WMI interface (and WMI call returns) expected
by the nvidia-wmi-ec-backlight interface. But the backlight class device
registered by the nvidia-wmi-ec-backlight driver does not actually work.

The amdgpu_bl0 native GPU backlight class device does actually work,
add a backlight=native DMI quirk for this.

Reported-by: Iris <pawel.js@protonmail.com>
Reviewed-by: Daniel Dadap <ddadap@nvidia.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
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Changes in v2:
- Add a comment that this needs to be revisited when dynamic-mux
  support gets added (suggested by: Daniel Dadap)