[llvm] PPC: Split 64bit target feature into 64bit and 64bit-support (PR #157206)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> I have bisected [a crash that folks have seen in the Linux kernel](https://lore.kernel.org/aM071XHb5cppdEKK@stanley.mountain/) to this change.

Fix in #159893 


https://github.com/llvm/llvm-project/pull/157206