pdc202xx_old: fix PIO mode setup

Fix the driver's tuneproc() method to always set the PIO mode requested and not
pick the best possible one, rename it to pdc202xx_tune_drive(), and change the
calls to it accordingly; remove the preceding comment which has nothing to do
with the code.

Sergei Shtylyov wrote:
>     The tuneproc() method should take arg 255 for auto-selecting the best PIO
> mode, not 5 as it did here + this driver's method always auto-selected instead
> of setting the mode it's been told to -- issue typical to drivers/ide/...

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