Please grep the remaining users, IMO you will find that's not really true. After your patch no core users remain, only ones in a few scattered drivers that most likely want your logic (or a simplified-for-that-controller version thereof).
That said if you want to be clearer we can hide the altstatus function
internally and only export an ata_sff_dma_sync() which does go *BANG* if
you call it with no altstatus (where you would immediately violate DMA
timing rules)
Want me to roll a patch in that style ?