[llvm] [BOLT][AArch64] Treat `br x30` as a return (PR #159458)

[YongKang Zhu via llvm-commits]

yozhu wrote:

`br x30` is used quite often in this assembly file: https://github.com/mozilla/mozjpeg/blob/master/simd/arm/aarch64/jsimd_neon.S

https://github.com/llvm/llvm-project/pull/159458