ivi-shell: Add shell-surface destructor.

>> No destructor function? So what happens, if the client unexpectedly
>> disconnects, and libwayland-server destroys all wl_resources in a
>> random order? I think you'd be leaking everything you allocated in
>> this function.

> [ntanibata] I will check and fix it.

Signed-off-by: Nobuhiko Tanibata <NOBUHIKO_TANIBATA@xddp.denso.co.jp>