This patch moves from using a hard coded number (4)

for the number of bytes in a particular instruction
to using
   const MCInstrDesc &Desc = MCII.get(TmpInst.getOpcode());
   Desc.getSize()

This is necessary with the advent of 16 bit instructions with
mips16 and micromips. It is also puts Mips in compliance with
the other targets for getting instruction size.

llvm-svn: 165171