[RL78] Fix encoding of divwu insn

[Kaushik Phatak]

Hi Nick,

> We appears to have different versions of this document.
> I have document number: R01US0015EJ0100 Rev.1.00 from Jan 31, 2011.

This is quite odd indeed. I too have the same document(R01US0015EJ0100 Rev.1.00)
which is dated Jan 31 2011.

The software manual currently available on their website also has 
a [0xCE 0xFB 0x0B] encoded for the DIVWU instruction and has no mention of 
a DIVH instruction.
http://documentation.renesas.com/doc/products/mpumcu/doc/rl78/r01us0015ej_rl78.pdf

We came across this issue while testing some code on the G14 target which 
supports this instruction and the hardware seemed to behave inconsistently. 
The updated toolchain with this patch seemed to resolve our problems.

Regards,
Kaushik