flash/nor: implement flash bank deallocation on OpenOCD exit

Change-Id: I8fcf09b2a85b3b68743f5fd68a31edea933b9b17
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/4414
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

src/openocd.c

@@ -353,6 +353,7 @@ int openocd_main(int argc, char *argv[])
 	/* Start the executable meat that can evolve into thread in future. */
 	ret = openocd_thread(argc, argv, cmd_ctx);
 
+	flash_free_all_banks();
 	gdb_service_free();
 	server_free();