docs: kvm: convert devices/vfio.txt to ReST

- Use standard title markup;
- adjust lists;
- mark code blocks as such.

Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Reviewed-by: Cornelia Huck <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>

Documentation/virt/kvm/devices/index.rst

···
    mpic
    s390_flic
    vcpu
+   vfio

Documentation/virt/kvm/devices/vfio.txt Documentation/virt/kvm/devices/vfio.rst

···
+.. SPDX-License-Identifier: GPL-2.0
+
+===================
 VFIO virtual device
 ===================
 
 Device types supported:
-  KVM_DEV_TYPE_VFIO
+
+  - KVM_DEV_TYPE_VFIO
 
 Only one VFIO instance may be created per VM.  The created device
 tracks VFIO groups in use by the VM and features of those groups
···
 	for the VFIO group.
   KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table
 	allocated by sPAPR KVM.
-	kvm_device_attr.addr points to a struct:
+	kvm_device_attr.addr points to a struct::
 
-	struct kvm_vfio_spapr_tce {
-		__s32	groupfd;
-		__s32	tablefd;
-	};
+		struct kvm_vfio_spapr_tce {
+			__s32	groupfd;
+			__s32	tablefd;
+		};
 
-	where
-	@groupfd is a file descriptor for a VFIO group;
-	@tablefd is a file descriptor for a TCE table allocated via
-		KVM_CREATE_SPAPR_TCE.
+	where:
+
+	- @groupfd is a file descriptor for a VFIO group;
+	- @tablefd is a file descriptor for a TCE table allocated via
+	  KVM_CREATE_SPAPR_TCE.