menuconfig: fix a regression when canceling the prompt dialog at exit

This commit fixes a bug, while introducing a new one..

commit 7203ddbd4be9720649e47d756a001e0c7d7f8ae2
Author: Wang YanQing <udknight@gmail.com>
Date:   Thu Jan 12 11:31:32 2012 +0800

    menuconfig: let make not report error when not save configuration

Pressing ESC should cancel the yes/no dialog and return back to
the main menu, but not exit from menuconfig.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Wang YanQing <udknight@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/kconfig/mconf.c

@@ -830,7 +830,8 @@ static int handle_exit(void)
 		fprintf(stderr, _("\n\n"
 				  "Your configuration changes were NOT saved."
 				  "\n\n"));
-		res = 0;
+		if (res != KEY_ESC)
+			res = 0;
 	}
 
 	return res;