MIPS: MSP71xx: Move code.

Now that Yosemite's gone we can move the MSP71xx code one level up.

Shane McDonald <mcdonald.shane@gmail.com>'s
https://patchwork.linux-mips.org/patch/4736/

 has been folded into this
patch.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>