This isn't something that ever changes between planes, so move it to
dpu_caps struct. Making this change will allow more re-use in the
"SSPP sub blocks config" part of the catalog, in particular when adding
support for SM8150 and SM8250 which have different max_linewidth.

This also sets max_hdeci_exp/max_vdeci_exp to 0 for sc7180, as decimation
is not supported on the newest DPU versions. (note that decimation is not
implemented, so this changes nothing)
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Signed-off-by: Rob Clark <robdclark@chromium.org>