drm/amd/display: handle DP2.0 RX with UHBR20 but not UHBR13.5 support

[why]
DP2.0 defines DP2.0 RX capability using bit maps. This means there is
a corner case the DP2.0 RX can declare UHBR20 capability but not UHBR13.5 support.
In this case we should skip UHBR13.5 selection and continue to our next option
in decide liink settings.

Reviewed-by: George Shen <George.Shen@amd.com>
Acked-by: Alan Liu <HaoPing.Liu@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>