drm/i915/dp_mst: Ensure link parameters are up-to-date for a disabled link

drm/i915/dp_mst: Ensure link parameters are up-to-date for a disabled link

As explained in the previous patch, the MST link BW reported by branch
devices during topology probing/path resources enumeration depends on
the link parameters programmed to DPCD to be up-to-date. After a sink is
plugged this is not ensured, as those DPCD values start out zeroed. The
target link parameters (for a subsequent modeset) are the maximum that
is supported, so make sure these maximum values are programmed before the
topology probing.

Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240722165503.2084999-14-imre.deak@intel.com