drm/msm/dp: move link-specific parsing from dp_panel to dp_link

drm/msm/dp: move link-specific parsing from dp_panel to dp_link

Since max_dp_lanes and max_dp_link_rate are link-specific parameters, move
their parsing from dp_panel to dp_link for better separation of concerns.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Xiangxu Yin <xiangxu.yin@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/675643/
Link: https://lore.kernel.org/r/20250919-add-displayport-support-for-qcs615-platform-v5-13-eae6681f4002@oss.qualcomm.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>