dt-bindings: msm: add DT bindings for sc7280

dt-bindings: msm: add DT bindings for sc7280

MSM Mobile Display Subsystem (MDSS) encapsulates sub-blocks
like DPU display controller, DSI, EDP etc. Add required DPU
device tree bindings for SC7280.

Signed-off-by: Krishna Manikandan <quic_mkrishn@quicinc.com>
Changes in v2:
  - Drop target from description (Stephen Boyd)
  - Drop items from compatible (Stephen Boyd)
  - Add clock names one per line for readability (Stephen Boyd)
  - Use correct indendation (Stephen Boyd)
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/1634738333-3916-1-git-send-email-quic_mkrishn@quicinc.com
Signed-off-by: Rob Clark <robdclark@chromium.org>