fesvr/htif: allow exit on SIGINT.

Currently signal handler would call exit() only on second received
signal, this prevent proper program cleanup.
Instead use signal flag to exit loop.

Signed-off-by: Volodymyr Fialko <vfialko@marvell.com>

fesvr/htif.cc

@@ -253,7 +253,7 @@ int htif_t::run()
     std::bind(enq_func, &fromhost_queue, std::placeholders::_1);
 
   if (tohost_addr == 0) {
-    while (true)
+    while (!signal_exit)
       idle();
   }