ipmi:pci: Blacklist a Realtek "IPMI" device

commit bc48fa1b upstream.

Realtek has some sort of "Virtual" IPMI device on the PCI bus as a
KCS controller, but whatever it is, it's not one.  Ignore it if seen.

[ Commit 13d0b35c (ipmi_si: Move PCI setup to another file) from Linux
  4.15-rc1 has not been back ported, so the PCI code is still in
  `drivers/char/ipmi/ipmi_si_intf.c`, requiring to apply the commit
  manually.

  This fixes a 100 s boot delay on the HP EliteDesk 705 G4 MT with Linux
  4.14.94. ]
Reported-by: Chris Chiu <chiu@endlessm.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Tested-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/char/ipmi/ipmi_si_intf.c

@@ -2447,6 +2447,15 @@ static int ipmi_pci_probe_regspacing(struct smi_info *info)
 	return DEFAULT_REGSPACING;
 }
 
+static struct pci_device_id ipmi_pci_blacklist[] = {
+	/*
+	 * This is a "Virtual IPMI device", whatever that is.  It appears
+	 * as a KCS device by the class, but it is not one.
+	 */
+	{ PCI_VDEVICE(REALTEK, 0x816c) },
+	{ 0, }
+};
+
 static int ipmi_pci_probe(struct pci_dev *pdev,
 				    const struct pci_device_id *ent)
 {
@@ -2454,6 +2463,9 @@ static int ipmi_pci_probe(struct pci_dev *pdev,
 	int class_type = pdev->class & PCI_ERMC_CLASSCODE_TYPE_MASK;
 	struct smi_info *info;
 
+	if (pci_match_id(ipmi_pci_blacklist, pdev))
+		return -ENODEV;
+
 	info = smi_info_alloc();
 	if (!info)
 		return -ENOMEM;