Don't probe for NEON with SIGILL on aarch64.

We assume that AArch64 systems are modern enough to have getauxval.

Change-Id: I4cc74f04ca5ed50b8ca1cfd00afeaaa01c6caca0
Reviewed-on: https://boringssl-review.googlesource.com/3280
Reviewed-by: Adam Langley <agl@google.com>
2 files changed