- Don't use ata_taskfiles cmd field for drive status reporting,
   we can now simply use drive->status instead.

 - Unify command type parser entries which could be unified due to the
   unification of corresponding interrupt handlers.

 - Eliminate reading parameter from ata_do_udma(). We have this information
   already in the rq. This allows us to merge several methods.

 - Rename XXX_udma to udma_setup, since we have finally settled up on this
   semantics.

 - Simplify tons of host chip code by removing wrapper functions.