ivi-layout: unmap desktop surfaces in ivi_view_destroy()

weston_desktop_surface_unlink_view() does now call weston_view_destroy() so the
weston_view is not destroyed here. This is a problem because the view remains in
the weston_layer view_list. If ivi_view_destroy() is called from
ivi_layout_surface_destroy() and the view list is rebuilt in the 'removed'
signal, then the list gets corrupted when the view is destroyed immediately
afterwards.
Fix this by calling weston_view_destroy() unconditionally for all view.

Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>