pci_host: change the signature of pci_data_{read, write}.

pci_host: change the signature of pci_data_{read, write}.

change the first argument, void *opaque to PCIBus *s
of the pci_data_{read, write}.
They aren't used as direct callback so the argument type
don't have to be void*. So change it to the right type.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>