media: platform: Use dev_err_probe instead of dev_err

It is possible that dma_request_chan will return EPROBE_DEFER,
which means that dma->xdev->dev is not ready yet. In this case,
dev_err(dma->xdev->dev), there will be no output. This patch
fixes the bug.

Signed-off-by: Wang Ming <machel@vivo.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>