arm64: dts: qcom: sdm660: Add required nodes for DSI1

Configure the second DSI host/phy and account for them in
the mmcc node.

Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20210728222542.54269-29-konrad.dybcio@somainline.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>