xen-pciback: fix INTERRUPT_TYPE_* defines

xen_pcibk_get_interrupt_type() assumes INTERRUPT_TYPE_NONE being 0
(initialize ret to 0 and return as INTERRUPT_TYPE_NONE).
Fix the definition to make INTERRUPT_TYPE_NONE really 0, and also shift
other values to not leave holes.
But also, do not assume INTERRUPT_TYPE_NONE being 0 anymore to avoid
similar confusions in the future.

Fixes: 476878e4 ("xen-pciback: optionally allow interrupt enable flag writes")
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

drivers/xen/xen-pciback/conf_space.c

@@ -320,7 +320,7 @@ int xen_pcibk_get_interrupt_type(struct pci_dev *dev)
 		if (val & PCI_MSIX_FLAGS_ENABLE)
 			ret |= INTERRUPT_TYPE_MSIX;
 	}
-	return ret;
+	return ret ?: INTERRUPT_TYPE_NONE;
 }
 
 void xen_pcibk_config_free_dyn_fields(struct pci_dev *dev)

drivers/xen/xen-pciback/conf_space.h

@@ -65,10 +65,10 @@ struct config_field_entry {
 	void *data;
 };
 
-#define INTERRUPT_TYPE_NONE (1<<0)
-#define INTERRUPT_TYPE_INTX (1<<1)
-#define INTERRUPT_TYPE_MSI  (1<<2)
-#define INTERRUPT_TYPE_MSIX (1<<3)
+#define INTERRUPT_TYPE_NONE (0)
+#define INTERRUPT_TYPE_INTX (1<<0)
+#define INTERRUPT_TYPE_MSI  (1<<1)
+#define INTERRUPT_TYPE_MSIX (1<<2)
 
 extern bool xen_pcibk_permissive;