PCI: Fix compile errors with PCI_ATS and !PCI_IOV

The ats and sroiv members of 'struct pci_dev' are required
for the ATS code already, even without IOV support compiled
in. So depend on ATS here. This is fine with PCI_IOV too
because it selects PCI_ATS. Also the prototypes for ATS
need to be available for PCI_ATS.

Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>