vduse: moving kvfree into caller

This free action should be moved into caller 'vduse_ioctl' in
concert with the allocation.

No functional change.

Signed-off-by: Guanjun <guanjun@linux.alibaba.com>
Link: https://lore.kernel.org/r/1638780498-55571-1-git-send-email-guanjun@linux.alibaba.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>