siimage: PIO mode setup fixes (take 2)

siimage: PIO mode setup fixes (take 2)

* Add sil_tuneproc() wrapper for siimage_tuneproc() which also sets
  PIO mode on the device.

* Add missing ide_get_best_pio_mode() call to sil_tuneproc() so
  "pio" == 255 (autotune) is handled correctly (previously PIO0 was used)
  and "pio" values > 4 && < 255 are filtered to PIO4 (instead of PIO0).

* Add code limiting maximum PIO mode according to the pair device capabilities
  to sil_tuneproc().

* Convert users of config_siimage_chipset_for_pio() to use sil_tune_pio() and
  sil_tuneproc().  This fixes PIO fallback in siimage_config_drive_for_dma() to
  use max PIO mode available instead of PIO4 (config_siimage_chipset_for_pio()
  used wrong arguments for ide_get_best_pio_mode() and as a results always
  tried to set PIO4).

* Remove no longer needed siimage_taskfile_timing()
  and config_siimage_chipset_for_pio().

* Enable ->autotune unconditionally and remove PIO tuning for UDMA/MDMA modes
  from siimage_speedproc()

* Bump driver version.

v2:
* Fix issues noticed by Sergei:
  - correct pair device check
  - trim only taskfile PIO to the slowest of the master/slave
  - enable ->autotune unconditionally and remove PIO tuning for UDMA/MDMA modes
    from siimage_speedproc()
  - add TODO item for IORDY bugs
  - minor cleanups

Reviewed-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>