drm/amdgpu/display: change pipe policy for DCN 2.1

drm/amdgpu/display: change pipe policy for DCN 2.1

BugLink: https://bugs.launchpad.net/bugs/1969107
commit 879791ad8bf3dc5453061cad74776a617b6e3319 upstream.

Fixes crash on MST Hub disconnect.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1849
Fixes: ee2698cf79cc ("drm/amd/display: Changed pipe split policy to allow for multi-display pipe split")
Signed-off-by: Benjamin Marty <info@benjaminmarty.ch>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 0115e4f2f6bc984bc8fdba41ada55f586dc28502)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>