arm64: dts: qcom: sc7280: split register block for DP controller

Follow the schema for the DP controller and declare 5 register regions
instead of using a single region for all the registers. Note, this
extends the dts by adding p1 region to the DP node (to be used for DP
MST).

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220710084133.30976-4-dmitry.baryshkov@linaro.org