drm/ingenic: Switch IPU plane to type OVERLAY

commit 68b433fe upstream.

It should have been an OVERLAY from the beginning. The documentation
stipulates that there should be an unique PRIMARY plane per CRTC.

Fixes: fc1acf31 ("drm/ingenic: Add support for the IPU")
Cc: <stable@vger.kernel.org> # 5.8+
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20210329175046.214629-2-paul@crapouillou.net


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>