usb: roles: fix include/linux/usb/role.h compile issue

when CONFIG_USB_ROLE_SWITCH is not defined,
add usb_role_switch_find_by_fwnode() definition which return NULL.

Fixes: c6919d5 ("usb: roles: Add usb_role_switch_find_by_fwnode()")
Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
Link: https://lore.kernel.org/r/1641818608-25039-1-git-send-email-quic_linyyuan@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/usb/role.h

@@ -91,6 +91,12 @@ fwnode_usb_role_switch_get(struct fwnode_handle *node)
 
 static inline void usb_role_switch_put(struct usb_role_switch *sw) { }
 
+static inline struct usb_role_switch *
+usb_role_switch_find_by_fwnode(const struct fwnode_handle *fwnode)
+{
+	return NULL;
+}
+
 static inline struct usb_role_switch *
 usb_role_switch_register(struct device *parent,
 			 const struct usb_role_switch_desc *desc)