drm/msm/dp: Stop using DP id as index in desc

In the SC8280XP platform there are two identical MDSS instances, each
with the same set of DisplayPort instances, at different addresses.

By not relying on the index to define the instance id it's possible to
describe them both in the same table and hence have a single compatible.

While at it, flatten the cfg/desc structure so that the match data is
just an array of descs.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/514397/
Link: https://lore.kernel.org/r/20221207220012.16529-6-quic_bjorande@quicinc.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>