drivers: dma: dma_nxp_edma: add function for channel filtering

The point of this commit is to allow users to request specific
channels. The following code snippet shows how this may now be
achieved:

	int requested_channel = 5;
	int ret = dma_request_channel(dev, &requested_channel);

Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>