Silence "Erratum 843419 found and fixed" info messages from gold.

BUG: 26536732

Tested by building binutils on ubuntu, and using the newly built gold
to link volantis binaries. The info messages are gone.

This patch is backported from upstream -

    commit e3dbf58233db3ad72f1ba624dc7f13ffd2728f25
    Author: Han Shen <shenhan@google.com>
    Date:   Thu Feb 11 09:47:49 2016 -0800

        Remove info message for every erratum 843419 found and fixed.

        2016-02-11 Rahul Chaudhry  <rahulchaudhry@google.com>

            * aarch64.cc (Target_aarch64::scan_erratum_843419_span):
            Remove info message for every erratum 843419 found and fixed.

Change-Id: I9792795096c919b006e98fdfdb01b448e597d605