This fixes a few problems in the vop crtc cleanup (handling error
paths and cleanup upon exit):

* The vop_create_crtc() error path had an unsafe version of the
  iterator used for iterating over all planes (though it was
  destroying planes in the iterator so should have used the safe
  version)

* vop_destroy_crtc() - wasn't calling vop_plane_destroy(), which made
  slub_debug unhappy, at least if we ended up running this due to a
  deferred probe.

* In vop_create_crtc() if we were missing the "port" device tree node
  we would fail but not return an error (found by code inspection).

Fix these problems.
Signed-off-by: Douglas Anderson <dianders@chromium.org>