dmaengine: of-dma: Fix of_dma_router_xlate's of_dma_xlate handling

dmaengine: of-dma: Fix of_dma_router_xlate's of_dma_xlate handling

of_dma_xlate callback can return ERR_PTR as well NULL in case of failure.

If error code is returned (not NULL) then the route should be released and
the router should not be registered for the channel.

Fixes: 54017cd102d09 ("dmaengine: of_dma: Support for DMA routers")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200806104928.25975-1-peter.ujfalusi@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>