[clang] [clang-tools-extra] [clang] Make 'fileScopeAsmDecl' matcher public (PR #165319)

[Davide Cunial via cfe-commits]

capitan-davide wrote:

Now unittest with `__asm` passed also for AArch64, I guess it was just a false positive.

https://github.com/llvm/llvm-project/pull/165319