vmm, pci, openapi: Add VFIO mmap BAR exclusion

Allow VFIO devices to list BAR indices that should not be
mmapped into the guest. This lets operators skip large BARs that
are known not to be used by their workload.

When a BAR is skipped, the log also calls out that P2P DMA
mapping is skipped because the VFIO DMA map path uses the same
mmap backing.

Signed-off-by: Damian Barabonkov <dbctl@pm.me>
Assisted-by: OpenCode:gpt-5.5

vmm/src/api/openapi/cloud-hypervisor.yaml

@@ -1223,6 +1223,11 @@ components:
         x_nv_gpudirect_clique:
           type: integer
           format: int8
+        x_exclude_mmap_bars:
+          type: array
+          items:
+            type: integer
+            format: int64
 
     UserDeviceConfig:
       required: