vdpa: Update sysfs ABI documentation

Fix the wrong drivers_autoprobe path name in the document

Signed-off-by: Shawn.Shao <shawn.shao@jaguarmicro.com>
Message-Id: <20230821011535.1117-1-shawn.shao@jaguarmicro.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>