MIPS: MSP71xx: Remove the RAMROOT functions

The RAMROOT function was a successful but non-portable attempt to append
the root filesystem to the end of the kernel image.  The preferred and
portable solution is to use an initramfs instead.

Signed-off-by: Shane McDonald <mcdonald.shane@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>