fix most of doxygen warnings and errors

openair3/NGAP/ngap_common.h

@@ -134,5 +134,6 @@ typedef int (*ngap_message_decoded_callback)(sctp_assoc_t assoc_id, uint32_t str
  @returns void
  **/
 void ngap_handle_criticality(NGAP_Criticality_t criticality);
+/** @}*/
 
 #endif /* NGAP_COMMON_H_ */

openair3/NGAP/ngap_gNB.h

@@ -31,7 +31,7 @@
 #include <stdio.h>
 #include <stdint.h>
 
-/** @defgroup _ngap_impl_ NGAP Layer Reference Implementation for gNB
+/** @defgroup _ngap_impl_ NGAP Layer Reference Implementation
  * @ingroup _ref_implementation_
  * @{
  */