usb: dwc2: Add brcm,bcm2708-usb compatible

When using CONFIG_OF_BOARD on rpi to use the dtb provided by the
RaspberryPi Fundation, the compatible string isn't the same, resulting
in not-functional usb from u-boot.

Signed-off-by: Oleksandr Tymoshenko <gonzo@FreeBSD.org>
Signed-off-by: Emmanuel Vadot <manu@freebsd.org>

drivers/usb/host/dwc2.c

@@ -1314,6 +1314,7 @@ struct dm_usb_ops dwc2_usb_ops = {
 
 static const struct udevice_id dwc2_usb_ids[] = {
 	{ .compatible = "brcm,bcm2835-usb" },
+	{ .compatible = "brcm,bcm2708-usb" },
 	{ .compatible = "snps,dwc2" },
 	{ }
 };