[llvm] Use BlockFrequency type in more places (NFC) (PR #68266)

[David Li via llvm-commits]

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@@ -26,10 +26,11 @@ class BlockFrequency {
   uint64_t Frequency;
 
 public:
-  BlockFrequency(uint64_t Freq = 0) : Frequency(Freq) { }
+  BlockFrequency() : Frequency(0) {}
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david-xl wrote:

remove this interface to make the intention (zero) clearer?

https://github.com/llvm/llvm-project/pull/68266