drm/amd/display: set lttpr mode before link settings

[Why]
Some lttpr devices do not work properly when lttpr mode is configured
after link settings.

[How]
Move lttpr configuration before lane settings.

Signed-off-by: abdoulaye berthe <abdoulaye.berthe@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>