[ForwardOpTree] Set DEBUG_TYPE to "polly-optree".

The previous value of "polly-delicm" was forgotten to to be changed when
ForwardOpTree was split from DeLICM.

Thanks to Tobias for noticing!

llvm-svn: 310465

polly/lib/Transform/ForwardOpTree.cpp

@@ -25,7 +25,7 @@
 #include "polly/ZoneAlgo.h"
 #include "llvm/Analysis/ValueTracking.h"
 
-#define DEBUG_TYPE "polly-delicm"
+#define DEBUG_TYPE "polly-optree"
 
 using namespace polly;
 using namespace llvm;