Add qcom,sc8280xp-edp to the list of eDP devices, unblocking `aux-bus'
property and fobidding `#sound-dai-cells' property. Also since
sc8280xp-edp, overriding sc8280xp-dp, will contain 5 reg resources, drop
the reg contraint (as it will become equivalent to the top-level one,
requiring min 4 and max 5 reg entries).

Fixes: b6f8c4de ("dt-bindings: msm/dp: Add SDM845 and SC8280XP compatibles")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Patchwork: https://patchwork.freedesktop.org/patch/518797/
Link: https://lore.kernel.org/r/20230118031718.1714861-1-dmitry.baryshkov@linaro.orgSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>