PCI/MSI: Fix msi_desc->affinity memory leak when freeing MSI IRQs

During device setup, msix_setup_entries() and msi_setup_entry() allocate
msi_desc by calling alloc_msi_entry().  alloc_msi_entry() can also allocate
a affinity cpumask.  During device teardown free_msi_irqs() is called and
the msi_desc is freed, but the affinity cpumask is leaked.

Fix it by calling free_msi_entry() which frees both the msi_desc and the
affinity cpumask.

[bhelgaas: aa48b6f7 ("genirq/MSI: Move alloc_msi_entry() from PCI into
 generic MSI code") moved alloc_msi_entry() from drivers/pci/msi.c to
 kernel/irq/msi.c and added a new corresponding free_msi_entry() interface.

 After aa48b6f7, pci/msi.c used alloc_msi_entry(), but did its own
 kfree() instead of using free_msi_entry().  28f4b041 ("genirq/msi: Add
 cpumask allocation to alloc_msi_entry") added affinity to both
 alloc_msi_entry() and free_msi_entry(), but pci/msi.c didn't use
 free_msi_entry(), resulting in this leak.]

Fixes: aa48b6f7 ("genirq/MSI: Move alloc_msi_entry() from PCI into generic MSI code")
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Myron Stowe <mstowe@redhat.com>