video: fbdev: pxa3xx_gcu: add devicetree bindings

Add a device tree match table for this hardware graphics acceleration
driver so it can be used by pxa3xx boards booted with a devicetree.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Reviewed-by: Robert Jarzmik <robert.jarzmik@free.fr>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>