[ARM64] Ensure arm64_be is dealt with when emitting debug info.

This is a partial port of r204816 (cpirker "Elf support for MC-JIT
runtime dynamic linker") from AArch64 to ARM64.
[ARM64] Try and make the ELF MCJIT *slightly* less broken for ARM64.

A bunch of switch cases were missing, not just for ARM64 but also for
AArch64_BE. I've fixed all those, but there's zero testing as
ExecutionEngine tests are disabled when crosscompiling and I don't
have a native platform available to test on.
[ARM64] Fix stupid copy-pasto in ARM64MCAsmInfo.cpp - aarch64_be -> arm64_be
[ARM64] Simplify if condition.

v2f32 and v4f32 were missed out of these conditions, so this is also
a bugfix.