FROMGIT: drm/i915/dp_mst: Enable LT fallback between UHBR/non-UHBR link rates

Enable switching between UHBR and non-UHBR link rates on MST links when
reducing the link parameters after an LT failure.

Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240722165503.2084999-15-imre.deak@intel.com
(cherry picked from commit 5c7b3934
 https://gitlab.freedesktop.org/drm/i915/kernel.git

 drm-intel-next)

BUG=b:332903004, b:322223603
TEST=Verify the link training fallback for UHBR<->non-UHBR rates

Change-Id: Ie300104550203fd3cca2a6113daef8c11f48232d
Signed-off-by: Rakshith M O <rakshith.m.o@intel.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/5802913


Reviewed-by: Manasi Navare <navaremanasi@chromium.org>
Reviewed-by: Charlton Lin <charlton.lin@intel.com>
Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Hubert Mazur <hmazur@google.com>