cmd64x: fix PIO mode setup (take 3)

The driver's tuneproc() method fails to set the drive's own speed -- fix this
by renaming the function to cmd64x_tune_pio(), making it return the mode set,
and "wrapping" the new tuneproc() method around it; while at it, also get rid
of the non-working prefetch control code (filtering out related argument values
in the "wrapper"), remove redundant PIO5 mode limitation, make cmdprintk() give
more sensible mode info, and remove mention about the obsolete /proc/ interface.
Get rid of the broken config_chipset_for_pio() which always tried to set PIO4,
switch to always auto-tuning PIO instead.
Oh, and add the missing PIO5 support to the speedproc() method while at it. :-)

Warning: compile tested only -- getting to the real hardware isn't that easy...

On Tuesday 06 February 2007 22:11, Mikael Pettersson <mikpe@it.uu.se> wrote:
> 
> Worked fine on my SPARC Ultra5 with a CMD646 IDE controller.

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