net/ieee802154: Expose a function to test for AR flag in net_pkt

This is both required in L2's radio part as well as it might be useful
on some ieee802154 radio drivers.

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>
diff --git a/include/net/ieee802154_radio.h b/include/net/ieee802154_radio.h
index a851c37..95ee25e 100644
--- a/include/net/ieee802154_radio.h
+++ b/include/net/ieee802154_radio.h
@@ -121,6 +121,16 @@
  */
 void ieee802154_init(struct net_if *iface);
 
+/**
+ * @brief Check if AR flag is set on the frame inside given net_pkt
+ *
+ * @param pkt A valid pointer on a net_pkt structure, must not be NULL.
+ *
+ * @return True if AR flag is set, False otherwise
+ */
+bool ieee802154_is_ar_flag_set(struct net_pkt *pkt);
+
+
 #ifdef __cplusplus
 }
 #endif