Minor defconfig change for S400 and MK908

- Using Ian Morrison's rknand enabled initramfs
- Disabled debug messages for rknand
- Enabled CONFIG_SCHED_AUTOGROUP, which should schedule tasks to give a
much better user experience (game changer according to Linus)
- Set DDR frequency to 500 MHz (tested by Galland on S400 and by
Omegamoon on MK908)
- Removed dummy localversion