PCI: Fix pci_enable_acs() support for the ACS quirks

There are ACS quirks that hijack the normal ACS processing and deliver to
to special quirk code. The enable path needs to call
pci_dev_specific_enable_acs() and then pci_dev_specific_acs_enabled() will
report the hidden ACS state controlled by the quirk.

The recent rework got this out of order and we should try to call
pci_dev_specific_enable_acs() regardless of any actual ACS support in the
device.

As before command line parameters that effect standard PCI ACS don't
interact with the quirk versions, including the new config_acs= option.

Link: https://lore.kernel.org/r/[e-mail]
Fixes: 47c8846a49ba ("PCI: Extend ACS configurability")
Reported-by: Jiri Slaby <[e-mail]>
Closes: https://lore.kernel.org/all/[e-mail]
Closes: https://bugzilla.suse.com/show_bug.cgi?id=1229019
Tested-by: Steffen Dirkwinkel <[e-mail]>
Signed-off-by: Jason Gunthorpe <[e-mail]>
Signed-off-by: Bjorn Helgaas <[e-mail]>

drivers/pci/pci.c

···
 static void pci_enable_acs(struct pci_dev *dev)
 {
 	struct pci_acs caps;
+	bool enable_acs = false;
 	int pos;
+
+	/* If an iommu is present we start with kernel default caps */
+	if (pci_acs_enable) {
+		if (pci_dev_specific_enable_acs(dev))
+			enable_acs = true;
+	}
 
 	pos = dev->acs_cap;
 	if (!pos)
···
 	pci_read_config_word(dev, pos + PCI_ACS_CTRL, &caps.ctrl);
 	caps.fw_ctrl = caps.ctrl;
 
-	/* If an iommu is present we start with kernel default caps */
-	if (pci_acs_enable) {
-		if (pci_dev_specific_enable_acs(dev))
-			pci_std_enable_acs(dev, &caps);
-	}
+	if (enable_acs)
+		pci_std_enable_acs(dev, &caps);
 
 	/*
 	 * Always apply caps from the command line, even if there is no iommu.