usb: dwc2: Add function for session B check

Add a new function to check the session B validity, to be use to check
cable connection.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Lukasz Majewski <lukma@denx.de>
diff --git a/include/usb/dwc2_udc.h b/include/usb/dwc2_udc.h
index 3cf20ea..8a426b6 100644
--- a/include/usb/dwc2_udc.h
+++ b/include/usb/dwc2_udc.h
@@ -27,4 +27,6 @@
 
 int dwc2_udc_probe(struct dwc2_plat_otg_data *pdata);
 
+int dwc2_udc_B_session_valid(struct udevice *dev);
+
 #endif	/* __DWC2_USB_GADGET */