Removed logic to flush lower half when cache is folded.
Added logic to reduce L1D misses when cache unfolds.

When the cache is unfolded, the upper tag and data banks
are copied into lower tag and data banks to reduce misses
due to cache unfolding.
TODO:
 - Figure out why the logic fails with number of sets set
to 64.
 - Figure out how to populate lower half of LRU table when
the cache unfolds.