Fix Idle Skipping in JitIL.

Has been broken since the flags-opt merge. The idle skipping code in
JitIL was very brittle and depended on the IL of it's inputs not
changing in any way.

flags-opt changed the IR generated by the cmp instruction, which is part
of the idle loop, causing JitIL to break in really weird ways, which
were almost impossible to track down.

This Fixes various wii games crashing/not booting and the Regspill
error on (all?) gamecube mmu games.

@JMC47 Could you do some testing on this?
Typo: optimization (or optimisation?)