PCI/MSI: Sanitize MSI-X table map handling

Unmapping the MSI-X base mapping in the loops which allocate/free MSI
descriptors is daft and in the way of allowing runtime expansion of MSI-X
descriptors.

Store the mapping in struct pci_dev and free it after freeing the MSI-X
descriptors.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20211206210224.871651518@linutronix.de

include/linux/pci.h

@@ -473,6 +473,7 @@ struct pci_dev {
 	u8		ptm_granularity;
 #endif
 #ifdef CONFIG_PCI_MSI
+	void __iomem	*msix_base;
 	const struct attribute_group **msi_irq_groups;
 #endif
 	struct pci_vpd	vpd;