cmd/internal/obj/sparc64: determine operand classes in preprocess
cmd/internal/obj/sparc64: determine operand classes in preprocess

Allows us to assemble trivial programs.

Change-Id: I38bca1df4f4578f27ab1e5373a7439347f29fe04

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