[clang] [Clang][AArch64] Remove unwarranted 'cannot be used in non-streaming mode' diagnostic. (PR #150592)

[Benjamin Maxwell via cfe-commits]

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@@ -5988,11 +5988,9 @@ bool clang::IsArmStreamingFunction(const FunctionDecl *FD,
     if (FD->hasAttr<ArmLocallyStreamingAttr>())
       return true;
 
-  if (const Type *Ty = FD->getType().getTypePtrOrNull())
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MacDue wrote:

> If for example, I were to call FD->dump() in this function, then dump will run into an assertion that the type is null. 

Any assumptions about like this should be backed by an explicit assert, dereferencing a null-pointer without an assert can lead to less obvious errors/issues (and it's not clear what the authors intent was).  

https://github.com/llvm/llvm-project/pull/150592