msi: fix MSI vector limit check in msi_set_mask()

MSI supports a maximum of PCI_MSI_VECTORS_MAX vectors - from 0 to
PCI_MSI_VECTORS_MAX - 1.

msi_set_mask() was previously using PCI_MSI_VECTORS_MAX as the upper
limit for MSI vectors. Fix the upper limit to PCI_MSI_VECTORS_MAX - 1.

Fixes: Coverity CID 1490141
Fixes: 08cf3dc vfio-user: handle device interrupts

Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Message-Id: <20220623153844.7367-1-jag.raman@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

hw/pci/msi.c

@@ -322,9 +322,9 @@ void msi_set_mask(PCIDevice *dev, int vector, bool mask, Error **errp)
     bool msi64bit = flags & PCI_MSI_FLAGS_64BIT;
     uint32_t irq_state, vector_mask, pending;
 
-    if (vector > PCI_MSI_VECTORS_MAX) {
+    if (vector >= PCI_MSI_VECTORS_MAX) {
         error_setg(errp, "msi: vector %d not allocated. max vector is %d",
-                   vector, PCI_MSI_VECTORS_MAX);
+                   vector, (PCI_MSI_VECTORS_MAX - 1));
         return;
     }