Thanks for your inputs.. I was able to generate kernel-ls1012a-rdb.itb and
boot LS1012ARDB with this image..
Procedure to generate kernel-ls1012a-rdb.itb
1. Enable and build to get mkimage and dtc tools
2. Add above tools paths to PATH variable
3. execute $mkimage -f kernel-ls1012a-rdb.its kernel-ls1012a-rdb.itb