dmaengine: fsl-edma: implement .device_synchronize callback

Implement .device_synchronize callback in order to be able to use
dmaengine_terminate_sync() and other primitives relying on said
callback.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: linux-imx@nxp.com
Cc: dmaengine@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Link: https://lore.kernel.org/r/20190731173659.14778-1-andrew.smirnov@gmail.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>