Functions in the DisplayPort code that relates to individual instances
(encoders) are passed both the struct msm_dp and the struct drm_encoder.
But in a situation where multiple DP instances would exist this means
that the caller need to resolve which struct msm_dp relates to the
struct drm_encoder at hand.

Store a reference to the struct msm_dp associated with each
dpu_encoder_virt to allow the particular instance to be associate with
the encoder in the following patch.
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211016221843.2167329-3-bjorn.andersson@linaro.orgSigned-off-by: Rob Clark <robdclark@chromium.org>