dmaengine: of: bail out early if "dmas" property is not present

And don't print an error: not configured is not an error.

Reported-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>