drm/msm/dp: Remove unused defines and members

Throughout the Qualcomm Displayport driver a number of defines and
struct members has become unused, but lingers in the code. Remove these.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/585345/
Link: https://lore.kernel.org/r/20240328-msm-dp-cleanup-v2-3-a5aed9798d32@quicinc.com


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