[test] Replace aarch64-*-eabi with aarch64

Also replace aarch64_be-*-eabi with aarch64_be

Using "eabi" for aarch64 targets is a common mistake and warned by Clang Driver.
We want to avoid it elsewhere as well. Just use the common "aarch64" without
other triple components.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D153943