poplar: add DWC2 OTG gadget support

It enables DWC2 OTG gadget driver support for Poplar board.  As
usb2_phy_init() is being always called from board_init(), we can save
the call from board_usb_init().

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/board/hisilicon/poplar/poplar.c b/board/hisilicon/poplar/poplar.c
index 8adc750..155dfbb 100644
--- a/board/hisilicon/poplar/poplar.c
+++ b/board/hisilicon/poplar/poplar.c
@@ -166,6 +166,34 @@
 	return ret;
 }
 
+#if defined(CONFIG_USB_GADGET) && defined(CONFIG_USB_GADGET_DWC2_OTG)
+#include <usb.h>
+#include <usb/dwc2_udc.h>
+#include <g_dnl.h>
+
+static struct dwc2_plat_otg_data poplar_otg_data = {
+	.regs_otg = HIOTG_BASE_ADDR
+};
+
+static void set_usb_to_device(void)
+{
+	setbits_le32(PERI_CTRL_USB3, USB2_2P_CHIPID);
+}
+
+int board_usb_init(int index, enum usb_init_type init)
+{
+	set_usb_to_device();
+	return dwc2_udc_probe(&poplar_otg_data);
+}
+
+int g_dnl_bind_fixup(struct usb_device_descriptor *dev, const char *name)
+{
+	if (!env_get("serial#"))
+		g_dnl_set_serialnumber("0123456789POPLAR");
+	return 0;
+}
+#endif
+
 int board_init(void)
 {
 	usb2_phy_init();