dmaengine: ep93xx: Fix a NULL vs IS_ERR() check in probe()

This was intended to be an IS_ERR() check, not a NULL check. The
ep93xx_dma_of_probe() function doesn't return NULL pointers.

Fixes: 4e8ad5ed845b ("dmaengine: cirrus: Convert to DT for Cirrus EP93xx")
Signed-off-by: Dan Carpenter <[e-mail]>
Reviewed-by: Alexander Sverdlin <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>

drivers/dma/ep93xx_dma.c

···
 	int ret;
 
 	edma = ep93xx_dma_of_probe(pdev);
-	if (!edma)
+	if (IS_ERR(edma))
 		return PTR_ERR(edma);
 
 	dma_dev = &edma->dma_dev;