vduse: add v1 API definition

This allows the kernel to detect whether the userspace VDUSE device
supports the VQ group and ASID features.  VDUSE devices that don't set
the V1 API will not receive the new messages, and vdpa device will be
created with only one vq group and asid.

The next patches implement the new feature incrementally, only enabling
the VDUSE device to set the V1 API version by the end of the series.

Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Xie Yongji <xieyongji@bytedance.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-3-eperezma@redhat.com>

Author: eugpermar

include/uapi/linux/vduse.h

@@ -10,6 +10,10 @@
 
 #define VDUSE_API_VERSION	0
 
+/* VQ groups and ASID support */
+
+#define VDUSE_API_VERSION_1	1
+
 /*
  * Get the version of VDUSE API that kernel supported (VDUSE_API_VERSION).
  * This is used for future extension.