ARM: dts: iwg20d-q7-common: Add LCD support

The iwg20d comes with a 7" capacitive touch screen, therefore
add support for it.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/1573660292-10629-11-git-send-email-fabrizio.castro@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>