cmd/link/internal/sparc64: remove XXX or replace it with TODO
cmd/link/internal/sparc64: remove XXX or replace it with TODO

Change-Id: I4104497a16b11e2a0771e64a71cd45bc7d5adc22

4ad/go,4ad/go,4ad/go,4ad/go,4ad/go,4ad/go,4ad/go,4ad/go