ARM: at91/dma: DMA controller registering with DT support

Device tree support on at91sam9g45 family SoC. Only call
platform_device_register() if no dma-controller node is
found in device tree.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>