Disable DPARCKEN in the DSCOMMAND0 register on the aic7890/91/96/97.
Parity checking is broken for some chip/MB combinations and this
is the work around recommended by Adaptec.
dpt_pci.c:
Remove a superflous '{' that prevented DPT_ALLOW_MEMIO from working.
pcireg.h:
Add a definition for Parity Error Reponse bit in the PCI Space
command register.