VT-d: split .ack and .disable DMA-MSI actors

Calling irq_complete_move() from .disable is wrong, breaking S3 resume.

Comparing with all other .ack actors, it was also missing a call to
move_{native,masked}_irq(). As the actor is masking its interrupt
anyway (albeit it's not immediately obvious why), the latter is the
better choice.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1039,8 +1039,6 @@ static void dma_msi_mask(struct irq_desc
     unsigned long flags;
     struct iommu *iommu = desc->action->dev_id;
 
-    irq_complete_move(desc);
-
     /* mask it */
     spin_lock_irqsave(&iommu->register_lock, flags);
     dmar_writel(iommu->reg, DMAR_FECTL_REG, DMA_FECTL_IM);
@@ -1053,6 +1051,13 @@ static unsigned int dma_msi_startup(stru
     return 0;
 }
 
+static void dma_msi_ack(struct irq_desc *desc)
+{
+    irq_complete_move(desc);
+    dma_msi_mask(desc);
+    move_masked_irq(desc);
+}
+
 static void dma_msi_end(struct irq_desc *desc, u8 vector)
 {
     dma_msi_unmask(desc);
@@ -1114,7 +1119,7 @@ static hw_irq_controller dma_msi_type = 
     .shutdown = dma_msi_mask,
     .enable = dma_msi_unmask,
     .disable = dma_msi_mask,
-    .ack = dma_msi_mask,
+    .ack = dma_msi_ack,
     .end = dma_msi_end,
     .set_affinity = dma_msi_set_affinity,
 };