Move properties common to all DPU DT nodes to the dpu-common.yaml.

Note, this removes description of individual DPU port@ nodes. However
such definitions add no additional value. The reg values do not
correspond to hardware INTF indices. The driver discovers and binds
these ports not paying any care for the order of these items. Thus just
leave the reference to graph.yaml#/properties/ports and the description.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/508384/
Link: https://lore.kernel.org/r/20221024164225.3236654-5-dmitry.baryshkov@linaro.orgSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>