Revert "[PGO] Fix computation of function Hash"

This reverts commit 7c298c1.
Fails make check-clang.

Failing Tests (8):
	Clang :: Profile/c-counter-overflows.c
	Clang :: Profile/c-general.c
	Clang :: Profile/c-unprofiled-blocks.c
	Clang :: Profile/cxx-rangefor.cpp
	Clang :: Profile/cxx-throws.cpp
	Clang :: Profile/misexpect-switch-default.c
	Clang :: Profile/misexpect-switch-nonconst.c
	Clang :: Profile/misexpect-switch.c

clang/lib/CodeGen/CodeGenPGO.cpp

@@ -747,15 +747,13 @@ uint64_t PGOHash::finalize() {
     return Working;
 
   // Check for remaining work in Working.
-  if (Working) {
-    using namespace llvm::support;
-    uint64_t Swapped = endian::byte_swap<uint64_t, little>(Working);
-    MD5.update(llvm::makeArrayRef((uint8_t *)&Swapped, sizeof(Swapped)));
-  }
+  if (Working)
+    MD5.update(Working);
 
   // Finalize the MD5 and return the hash.
   llvm::MD5::MD5Result Result;
   MD5.final(Result);
+  using namespace llvm::support;
   return Result.low();
 }