dmaengine: OF DMAEngine API based on CONFIG_DMA_OF instead of CONFIG_OF

5fa422c9 ("dmaengine: move drivers/of/dma.c -> drivers/dma/of-dma.c")
moved OF base DMAEngine code to of-dma.c, then it based on CONFIG_DMA_OF.
But, OF base DMAEngine API on of_dma.h still based on CONFIG_OF now.
So, current kernel can't find OF base DMAEngine API if .config has CONFIG_OF,
but not have CONFIG_DMA_OF. This patch tidyup it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>