dmaengine: fsl-edma: fix wrong pointer check in fsl_edma3_attach_pd()

device_link_add() returns NULL pointer not PTR_ERR() when it fails,
so replace the IS_ERR() check with NULL pointer check.

Fixes: 72f5801a4e2b ("dmaengine: fsl-edma: integrate v3 support")
Signed-off-by: Yang Yingliang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/fsl-edma-main.c

···
 		link = device_link_add(dev, pd_chan, DL_FLAG_STATELESS |
 					     DL_FLAG_PM_RUNTIME |
 					     DL_FLAG_RPM_ACTIVE);
-		if (IS_ERR(link)) {
-			dev_err(dev, "Failed to add device_link to %d: %ld\n", i,
-				PTR_ERR(link));
+		if (!link) {
+			dev_err(dev, "Failed to add device_link to %d\n", i);
 			return -EINVAL;
 		}