drm/amd/display: Fix phy id mapping issue for secure display

[Why]
Under mst scenario, mst streams are from the same link_enc_hw_inst.
As the result, can't utilize that as the phy index for distinguising
different stream sinks.

[How]
Sort the connectors by:
link_enc_hw_instance->mst tree depth->mst RAD

After sorting the phy index assignment, store connector's relevant info
into dm mapping array. Once need the index, just look up the static
array.

Reviewed-by: HaoPing Liu <haoping.liu@amd.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>