PCI/MSI: Move pci_msix_vec_count() to api.c

To disentangle the maze in msi.c, all exported device-driver MSI APIs are
now to be grouped in one file, api.c.

Move pci_msix_vec_count() and make its kernel-doc comprehensive.
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20221111122015.099461602@linutronix.de

drivers/pci/msi/api.c

@@ -59,6 +59,26 @@ void pci_disable_msi(struct pci_dev *dev)
 }
 EXPORT_SYMBOL(pci_disable_msi);
 
+/**
+ * pci_msix_vec_count() - Get number of MSI-X interrupt vectors on device
+ * @dev: the PCI device to operate on
+ *
+ * Return: number of MSI-X interrupt vectors available on this device
+ * (i.e., the device's MSI-X capability structure "table size"), -EINVAL
+ * if the device is not MSI-X capable, other errnos otherwise.
+ */
+int pci_msix_vec_count(struct pci_dev *dev)
+{
+	u16 control;
+
+	if (!dev->msix_cap)
+		return -EINVAL;
+
+	pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &control);
+	return msix_table_size(control);
+}
+EXPORT_SYMBOL(pci_msix_vec_count);
+
 /**
  * pci_enable_msix_range() - Enable MSI-X interrupt mode on device
  * @dev:     the PCI device to operate on

drivers/pci/msi/msi.c

@@ -701,26 +701,6 @@ void pci_msi_shutdown(struct pci_dev *dev)
 	pcibios_alloc_irq(dev);
 }
 
-/**
- * pci_msix_vec_count - return the number of device's MSI-X table entries
- * @dev: pointer to the pci_dev data structure of MSI-X device function
- * This function returns the number of device's MSI-X table entries and
- * therefore the number of MSI-X vectors device is capable of sending.
- * It returns a negative errno if the device is not capable of sending MSI-X
- * interrupts.
- **/
-int pci_msix_vec_count(struct pci_dev *dev)
-{
-	u16 control;
-
-	if (!dev->msix_cap)
-		return -EINVAL;
-
-	pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &control);
-	return msix_table_size(control);
-}
-EXPORT_SYMBOL(pci_msix_vec_count);
-
 static int __pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries,
 			     int nvec, struct irq_affinity *affd, int flags)
 {