cifs: smb2_clone_range() - exit on unhandled error

While attempting to clone a file on a samba server, we receive a
STATUS_INVALID_DEVICE_REQUEST. This is mapped to -EOPNOTSUPP which
isn't handled in smb2_clone_range(). We end up looping in the while loop
making same call to the samba server over and over again.

The proposed fix is to exit and return the error value when encountered
with an unhandled error.

Cc: <stable@vger.kernel.org>
Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Signed-off-by: Steve French <steve.french@primarydata.com>
Signed-off-by: Steve French <smfrench@gmail.com>