Remove pci_ats_enabled().  There are no callers outside the ATS code
itself.  We don't need to check ats_cap, because if we don't find an ATS
capability, we'll never set ats_enabled.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NJoerg Roedel <jroedel@suse.de>