drm/amd/display: Remove the unused variable ds_port

Variable ds_port is not effectively used, so delete it.

drivers/gpu/drm/amd/amdgpu/../display/dc/link/protocols/link_dp_capability.c:280:35: warning: variable ‘ds_port’ set but not used.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=4030


Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>