mount using nfs4 giving no such device error

Solved the problem after 3 days!!

I tried mounting the nfs4 server folder from a client with a newer Kernel version (3.8). I was able to do so. So I copied the configuration file /boot/configure-3.8-generic file to my /usr/src/.config, and enabled the option Filesystems -> Network File Systems -> NFS3 client load as module and NFS4 client load as module.

compiled my kernel again, created initrd image, updated grub, and now I am able to mount the server folder from my 2.6 kernel client also!