Interpreter: Fix bug with icache emulation.

The constructor sets up way_from_valid and way_from_plur as fast lookup
tables for implementing the PLRU algrothm. Then the Init function
memsets them to zero, meaning the instruction cache will now always
choose the first way in each set.

This degrades the cache from 128 sets, 8 way to 128 sets, 1 way.

Not only does fixing this bug increase accuracy, but it increases
preformance too, giving a 1% speedup to interpreter.

Source/Core/Core/PowerPC/PPCCache.cpp

@@ -71,8 +71,6 @@ namespace PowerPC
 	{
 		memset(data, 0, sizeof(data));
 		memset(tags, 0, sizeof(tags));
-		memset(way_from_valid, 0, sizeof(way_from_valid));
-		memset(way_from_plru, 0, sizeof(way_from_plru));
 
 		Reset();
 	}