sata_promise: fix error decode regression

Promise ATA ports should always be reset by pdc_reset_port()
when errors are detected, but the recent error reason decoding
update to sata_promise replaced that reset with a freeze.

This patch changes the error detection to do a reset again.
This makes the error decoding update safer, as it now only
adds error decoding without changing any other behaviour.

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Jeff Garzik <jeff@garzik.org>