In order to align ppc64le with the existing code, 4467e59b changed the
prefix for both the ARM and ppc64le AES assembly code to be “aes_hw_”.
However, it didn't update aes.c as well.

Change-Id: I8e3c7dea1c49ddad8a613369af274e25d572a8fd
Reviewed-on: https://boringssl-review.googlesource.com/11342
Reviewed-by: Adam Langley <agl@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>