[llvm] [BPF] Make llvm-objdump disasm default cpu v4 (PR #102166)

[via llvm-commits]

yonghong-song wrote:

@4ast PPC used a cpu 'future' so they do not need to update tryGetCPUName(). Do we need to add a 'latest' cpu flavor to avoid updating tryGetCPUName()? I am not 100% sure about this since we may update tryGetCPUName() very infrequently as we do not increase cpu number very often. WDYT?

https://github.com/llvm/llvm-project/pull/102166