drm/amd/display: allow DP40 cables to do UHBR13.5

why:
With DP2.1a expansion we are allowing DP40 cables to do UHBR13.5

how:
Assume UHBR10 means UHBR13.5 also for unknown cable type and
passive cable type.

Reviewed-by: George Shen <george.shen@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Ran Shi <ran.shi@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>