Major changes to Cortex-A9 itinerary.

1. Model dual issues as two FUs.
2. Model the pipelines correctly: two symmetric ALUs, the multiplier is a
   dependent pipeline on ALU0.
The changes do not have much impact on codegen right now. But I plan to make
pre-RA scheduler multi-issue aware which should take good advantage of the
changes.

llvm-svn: 115457