After looking into the HPT370 manual (now that I have it) and re-checking all
the timing tables, here's what I have discovered:

- at 33 MHz clock, PIO mode 0 timings turned to be overclocked, and all other
  PIO modes underclocked;

- at 50 MHz clock, PIO modes 0 to 2 turned to be overclocked;

- at 66 MHz clock, PIO mode 0 was overclocked too.

Finally, the taskfile timing (matching PIO mode 0) turned to be overclocked at
all clock frequencies (and in all manuals)...

The new timings have been tested on HPT370 chip (at 33 MHz PCI clock) and on
HPT371N chip (at both 50 and 66 MHz DPLL clock).

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