Integrate linux-seco-rk/feature/nfs-boot
[E09][KERNEL] E09R-80 Add NFS support
Add to the defconfig the configuration flags to enable the support
of all versions of NFS on boot.
NOTE: The flag CONFIG_ROOT_NFS is required for all the NFS versions in
order to let the kernel know how to handle the network file system.
If this flag is not set, kernel panic occurs.