monitor: Fix HMP tab completion

Commands with multiple boolean flag options (like 'info block') didn't
provide correct completion because only the first one was skipped.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

monitor.c

@@ -4695,7 +4695,7 @@ static void monitor_find_completion_by_table(Monitor *mon,
             }
         }
         str = args[nb_args - 1];
-        if (*ptype == '-' && ptype[1] != '\0') {
+        while (*ptype == '-' && ptype[1] != '\0') {
             ptype = next_arg_type(ptype);
         }
         switch(*ptype) {