[vector] Add ref to AArch64 in module info

[Paul Sandoz]

Hi,

Please review the following small change to add a reference to AArch64 in the module info:

  http://cr.openjdk.java.net/~psandoz/panama/vector-module-AArch64-ref/webrev/ <http://cr.openjdk.java.net/~psandoz/panama/vector-module-AArch64-ref/webrev/>

This change is in response to reviews in preparation for integration into jdk/jdk.

Paul.