cmd/internal/obj/sparc64: add the type to map keys in optab
cmd/internal/obj/sparc64: add the type to map keys in optab

This is required because we need to be able to compile cmd/internal/obj/...
with Go 1.4, for bootstrapping.

Change-Id: Icb903b1a509bfe63a897a277e8010cdf222a91c4

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