ivi-shell: remove ivi_layout_get_screen_output API

The controller plugins use IVI Layout API with weston outputs.
Therefore, this API is not required.

Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Acked-by: Wataru Natsume <wnatsume@jp.adit-jv.com>