UefiCpuPkg/MtrrLib: Fix unit test read overflow

Change conditional check to check the array index before
reading the array member to prevent read pas end of buffer.

Signed-off-by: Michael D Kinney <[email protected]>

UefiCpuPkg/Library/MtrrLib/UnitTest/Support.c

@@ -745,7 +745,7 @@ GetNextDifferentElementInSortedArray (
   UINT64  CurrentElement;
 
   CurrentElement = Array[Index];
-  while (CurrentElement == Array[Index] && Index < Count) {
+  while (Index < Count && CurrentElement == Array[Index]) {
     Index++;
   }