xen: Remove redundant initialization of irq

The variable irq is being initialized with a value that is never read
and it is being updated later with a new value.  The initialization is
redundant and can be removed.

Addresses-Coverity: ("Unused value")
Link: https://lore.kernel.org/r/20200611123134.922395-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

arch/x86/pci/xen.c

@@ -62,7 +62,7 @@ static int xen_pcifront_enable_irq(struct pci_dev *dev)
 #ifdef CONFIG_ACPI
 static int xen_register_pirq(u32 gsi, int triggering, bool set_pirq)
 {
-	int rc, pirq = -1, irq = -1;
+	int rc, pirq = -1, irq;
 	struct physdev_map_pirq map_irq;
 	int shareable = 0;
 	char *name;