[gold][aarch64] Silence info message for every erratum 843419 found and fixed

[Cary Coutant]

> 2016-02-05 Rahul Chaudhry  <rahulchaudhry@google.com>
>
>         * aarch64.cc (Target_aarch64::scan_erratum_843419_span): Remove
>         info message for every erratum 843419 found and fixed.
>
>
> Ok for trunk?

This is OK with me if it's OK with Han.

-cary