drm/amd/display: Change function decide_dp_link_settings to avoid infinite looping

drm/amd/display: Change function decide_dp_link_settings to avoid infinite looping

Why:
Function decide_dp_link_settings() loops infinitely when required bandwidth
can't be supported.

How:
Check the required bandwidth against verified_link_cap before trying to
find a link setting for it.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Bing Guo <bing.guo@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Anson Jacob <anson.jacob@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>