xen/irq: If we fail during msi_capability_init return proper error code.

There are three different modes: PV, HVM, and initial domain 0. In all
the cases we would return -1 for failure instead of a proper error code.
Fix this by propagating the error code from the generic IRQ code.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 1017c7b..11a9301 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -175,8 +175,10 @@
 					       "pcifront-msi-x" :
 					       "pcifront-msi",
 						DOMID_SELF);
-		if (irq < 0)
+		if (irq < 0) {
+			ret = irq;
 			goto free;
+		}
 		i++;
 	}
 	kfree(v);
@@ -221,8 +223,10 @@
 		if (msg.data != XEN_PIRQ_MSI_DATA ||
 		    xen_irq_from_pirq(pirq) < 0) {
 			pirq = xen_allocate_pirq_msi(dev, msidesc);
-			if (pirq < 0)
+			if (pirq < 0) {
+				irq = -ENODEV;
 				goto error;
+			}
 			xen_msi_compose_msg(dev, pirq, &msg);
 			__write_msi_msg(msidesc, &msg);
 			dev_dbg(&dev->dev, "xen: msi bound to pirq=%d\n", pirq);
@@ -244,7 +248,7 @@
 error:
 	dev_err(&dev->dev,
 		"Xen PCI frontend has not registered MSI/MSI-X support!\n");
-	return -ENODEV;
+	return irq;
 }
 
 #ifdef CONFIG_XEN_DOM0