arm64: qcom: sc7280-herobrine: Enable DP

This enables DisplayPort for herobrine boards.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220513065704.1.I9b9b9d4d1a3e0350a89221892261881a1771ad15@changeid