alim15x3: fix PIO timings calculations

Just use the standard ide_timing_compute() helper to calculate
PIO timings.  This fixes many issues with the open-coded version
like potential recovery timings underclocking or not accounting
for the enhanced cycle time specified by the device.

Based on libata pata_ali host driver.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>