usb: renesas_usbhs: add support for requesting DT DMA

This patch adds dma_request_slave_channel_reason() calling to request
dma slave channels for multiplatform environment.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Documentation/devicetree/bindings/usb/renesas_usbhs.txt

@@ -14,6 +14,8 @@ Optional properties:
 			 function should be enabled
   - phys: phandle + phy specifier pair
   - phy-names: must be "usb"
+  - dmas: Must contain a list of references to DMA specifiers.
+  - dma-names : Must contain a list of DMA names, "tx" or "rx".
 
 Example:
 	usbhs: usb@e6590000 {

drivers/usb/renesas_usbhs/fifo.c

@@ -1069,12 +1069,21 @@ static void usbhsf_dma_init_pdev(struct usbhs_fifo *fifo)
 					    &fifo->rx_slave);
 }
 
+static void usbhsf_dma_init_dt(struct device *dev, struct usbhs_fifo *fifo)
+{
+	fifo->tx_chan = dma_request_slave_channel_reason(dev, "tx");
+	fifo->rx_chan = dma_request_slave_channel_reason(dev, "rx");
+}
+
 static void usbhsf_dma_init(struct usbhs_priv *priv,
 			    struct usbhs_fifo *fifo)
 {
 	struct device *dev = usbhs_priv_to_dev(priv);
 
-	usbhsf_dma_init_pdev(fifo);
+	if (dev->of_node)
+		usbhsf_dma_init_dt(dev, fifo);
+	else
+		usbhsf_dma_init_pdev(fifo);
 
 	if (fifo->tx_chan || fifo->rx_chan)
 		dev_dbg(dev, "enable DMAEngine (%s%s%s)\n",