dt-bindings: msm/dp: Add DP compatible strings for sc7280

dt-bindings: msm/dp: Add DP compatible strings for sc7280

The Qualcomm SC7280 platform supports one eDP controller
and a DP controller. This change will add the compatible
string for both eDP and DP to msm dp-controller binding.

Signed-off-by: Sankeerth Billakanti <quic_sbillaka@quicinc.com>
changes in v3:
    - Modify the subject (Doug Anderson)
    - Add sc7280-dp also to the list (Stephen Boyd)

changes in v2:
    - Sort alphabetically (Stephen Boyd)
    - Cleanup residual stale changes in the patch (Matthias Kaehlcke)
    - Modify the subject (Doug Anderson)
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/1635839325-401-2-git-send-email-quic_sbillaka@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>