drm/amd/display: link link_dp_dpia_bw.o in makefile

[Why & How]
- We have added link_dp_dpia_bw code but it is not currently
added in makefile. We are adding this to makefile so it would
be built.
- Remove unused dc_link.h

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@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>