cmd64x: fix multiword and remove single-word DMA support

Fix the multiword DMA and drop the single-word DMA support (which nobody will
miss, I think).  In order to do it, a number of changes was necessary:

- rename program_drive_counts() to program_cycle_times(), pass to it cycle's
  total/active times instead of the clock counts, and convert them into the
  active/recovery clocks there instead of cmd64x_tune_pio() -- this causes
  quantize_timing() to also move;

- contrarywise, move all the code handling the address setup timing into
  cmd64x_tune_pio(), so that setting MWDMA mode wouldn't change address setup;

- remove from the speedproc() method the  bogus code pretending to set the DMA
  timings by twiddling bits in the BMIDE status register, handle setting MWDMA
  by just calling program_cycle_times(); while at it, improve the style of that
  whole switch statement;

- stop fiddling with the DMA capable bits in the speedproc() method -- they do
  not enable DMA, and are properly dealt with by the dma_host_{on,off} methods;

- don't set hwif->swdma_mask in the init_hwif() method anymore.

In addition to those changes, do the following:

- in cmd64x_tune_pio(), when writing to ARTTIM23 register preserve the interrupt
  status bit, eliminate local_irq_{save|restore}() around this code as there's
  *no* actual race with the interrupt handler, and move cmdprintk() to a more
  fitting place -- after ide_get_best_pio_mode() call;

- make {arttim|drwtim}_regs arrays single-dimensional, indexed with drive->dn;

- rename {setup|recovery}_counts[] into more fitting {setup|recovery}_values[];

- in  the speedproc() method, get rid of the duplicate reads/writes from/to the
  UDIDETCRx registers and of the extra variable used to store the transfer mode
  value after filtering,  use another method of determining master/slave drive,
  and cleanup useless parens;

- beautify cmdprintk() output here and there.

While at it, remove meaningless comment about the driver being used only on
UltraSPARC and long non-relevant RCS tag. :-)
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>