vdpa: Add missing comment for virtqueue count

stable inclusion
from stable-v5.11
commit 476c135e
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WXCZ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=476c135e321716ad7a8a5d4a19a636e2dcc50526

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Add missing comment for number of virtqueue.
Signed-off-by: NParav Pandit <parav@nvidia.com>
Reviewed-by: NEli Cohen <elic@nvidia.com>
Acked-by: NJason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20201112064005.349268-2-parav@nvidia.comSigned-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NPengyuan Zhao <zhaopengyuan@hisilicon.com>

include/linux/vdpa.h

@@ -44,6 +44,7 @@ struct vdpa_mgmt_dev;
  * @config: the configuration ops for this device.
  * @index: device index
  * @features_valid: were features initialized? for legacy guests
+ * @nvqs: maximum number of supported virtqueues
  */
 struct vdpa_device {
 	struct device dev;