drm/amd/display: Fix DP MST sinks removal issue

drm/amd/display: Fix DP MST sinks removal issue

[ Upstream commit cbd6c1b17d3b42b7935526a86ad5f66838767d03 ]

[Why]
In USB4 DP tunneling, it's possible to have this scenario that
the path becomes unavailable and CM tears down the path a little bit late.
So, in this case, the HPD is high but fails to read any DPCD register.
That causes the link connection type to be set to sst.
And not all sinks are removed behind the MST branch.

[How]
Restore the link connection type if it fails to read DPCD register.

Cc: stable@vger.kernel.org
Cc: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Cruise Hung <Cruise.Hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit cbd6c1b17d3b42b7935526a86ad5f66838767d03)
Modified for stable backport as a lot of the code in this file was moved
in 6.3 to drivers/gpu/drm/amd/display/dc/link/link_detection.c.
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>