[di] Now that DI and PMO are split, debride some dead code.

Specifically isDefiniteInitFinished is always set to false and
TreatAddressToPointerAsInout is set to true when ever DI is run, so this patch
just constant propagates those values and then DCEs as appropriate.

lib/SILOptimizer/Mandatory/DefiniteInitialization.cpp

@@ -2888,8 +2888,7 @@ static void processMemoryObject(MarkUninitializedInst *I) {
   DIElementUseInfo UseInfo;
 
   // Walk the use list of the pointer, collecting them into the Uses array.
-  collectDIElementUsesFrom(MemInfo, UseInfo, false,
-                           /*TreatAddressToPointerAsInout*/ true);
+  collectDIElementUsesFrom(MemInfo, UseInfo);
 
   LifetimeChecker(MemInfo, UseInfo).doIt();
 }