UBUNTU: SAUCE: drm/i915: Force DPCD backlight mode for Dell XPS 9510(TGL)

UBUNTU: SAUCE: drm/i915: Force DPCD backlight mode for Dell XPS 9510(TGL)

BugLink: https://bugs.launchpad.net/bugs/1933566
DELL XPS 9510 OLED panel needs DPCD to get control of backlight.
Kernel 5.12+ support the backlight via:
commit: <4a8d79901d5b> ("drm/i915/dp: Enable Intel's HDR backlight interface (only SDR for now)")
Only make backlight work on lower versions of kernel.

Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
[KelseyS: context changes to apply patch since adid_quirk_list has since
changed. No changes to the added line.]
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>