usb: musb: cppi41: allow it to work again

since commit 33c300cb90a6 ("usb: musb: dsps:
don't fake of_node to musb core") we have been
preventing CPPI 4.1 from probing due to NULL
of_node. We can't revert said commit otherwise
a different regression would show up, so the fix
is to look for the parent device's (glue layer's)
of_node instead, since that's the thing which
is actually described in DTS.

Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_cppi41.c

@@ -614,7 +614,7 @@ static int cppi41_dma_controller_start(struct cppi41_dma_controller *controller)
 {
 	struct musb *musb = controller->musb;
 	struct device *dev = musb->controller;
-	struct device_node *np = dev->of_node;
+	struct device_node *np = dev->parent->of_node;
 	struct cppi41_dma_channel *cppi41_channel;
 	int count;
 	int i;
@@ -664,7 +664,7 @@ static int cppi41_dma_controller_start(struct cppi41_dma_controller *controller)
 		musb_dma->status = MUSB_DMA_STATUS_FREE;
 		musb_dma->max_len = SZ_4M;
 
-		dc = dma_request_slave_channel(dev, str);
+		dc = dma_request_slave_channel(dev->parent, str);
 		if (!dc) {
 			dev_err(dev, "Failed to request %s.\n", str);
 			ret = -EPROBE_DEFER;
@@ -695,7 +695,7 @@ cppi41_dma_controller_create(struct musb *musb, void __iomem *base)
 	struct cppi41_dma_controller *controller;
 	int ret = 0;
 
-	if (!musb->controller->of_node) {
+	if (!musb->controller->parent->of_node) {
 		dev_err(musb->controller, "Need DT for the DMA engine.\n");
 		return NULL;
 	}