[Why & How] All dc subcomponents should call another dc component via function pointers stored in a component structure. This is part of dc coding convention since the beginning. The reason behind this is to improve encapsulation and polymorphism. The function contract is extracted into a single link service structure defined in link.h header file and implemented only in link_factory.c instead of spreading across multiple files in link component file structure. 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>