drm/amd/display: Limit max link cap with LTTPR caps

drm/amd/display: Limit max link cap with LTTPR caps

[Why]
Max link rate should be limited to the maximum link rate support by any
LTTPR that are connected, including when operating in transparent mode.

[How]
Include transparent mode when factoring in LTTPR max supported link
rate.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Wesley Chalmers <wesley.chalmers@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: George Shen <George.Shen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>