[AArch64] Correct v9.x-a Features

A change to D109517 during review stated it was disabling the crypto
extensions by default in armv9a, but it also ended up removing two other
non-crypto features: i8mm and bf16. This error was also made in D116158.

This patch re-adds those two extensions to the feature bitmaps for the
affected armv9a versions in the target parser.

Differential Revision: https://reviews.llvm.org/D134647