drm/amd/display: Cache streams targeting link when performing LT automation

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Cache streams targeting link when performing LT automation [WHY] Last LT automation update can cause crash by referencing current_state and calling into dc_update_planes_and_stream which may clobber current_state. [HOW] Cache relevant stream pointers and iterate through them instead of relying on the current_state.