added warning to -h that active monitor mode is broken on many mt76 drivers

Author: =

hcxdumptool.c

@@ -5482,6 +5482,7 @@ fprintf(stdout, "%s %s  (C) %s ZeroBeat\n"
 	"                    default %d seconds\n"
 	"-A               : ACK incoming frames\n"
 	"                    INTERFACE must support active monitor mode\n"
+	"                    Warning: active monitor mode is broken on many mt76 drivers\n"
 	"-L               : show PHYSICAL INTERFACE list and terminate\n"
 	"-l               : show PHYSICAL INTERFACE list (tabulator separated and greppable) and terminate\n"
 	"-I <INTERFACE>   : show detailed information about INTERFACE and terminate\n"