SMB3: Rename clone_range to copychunk_range

Server side copy is one of the most important mechanisms smb2/smb3
supports and it was unintentionally disabled for most use cases.

Renaming calls to reflect the underlying smb2 ioctl called. This is
similar to the name duplicate_extents used for a similar ioctl which is
also used to duplicate files by reusing fs blocks. The name change is to
avoid confusion.

Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>