LinuxKPI: add skeleton pci_enable_wake()

Given we do not yet support "wake" bits in device there is little need
doing it in PCI if we cannot check if we are supposed to do the
operation in first place.  Once we would implement this, we would need
to also do the appropriate PCI (pme) checks before enabling (disabling)
it.

MFC after:	3 days
Reviewed by:	dumbbell
Differential Revision: https://reviews.freebsd.org/D53208

sys/compat/linuxkpi/common/include/linux/pci.h

@@ -831,6 +831,19 @@ lkpi_pci_restore_state(struct pci_dev *pdev)
 #define pci_save_state(dev)	lkpi_pci_save_state(dev)
 #define pci_restore_state(dev)	lkpi_pci_restore_state(dev)
 
+static inline int
+linuxkpi_pci_enable_wake(struct pci_dev *pdev, pci_power_t state, bool ena)
+{
+	/*
+	 * We do not currently support this in device.h either to
+	 * check if the device is allowed to wake up in first place.
+	 */
+	pr_debug("%s: TODO\n", __func__);
+	return (0);
+}
+#define	pci_enable_wake(dev, state, ena)				\
+    linuxkpi_pci_enable_wake(dev, state, ena)
+
 static inline int
 pci_reset_function(struct pci_dev *pdev)
 {