[gold][aarch64]Patch to fix a tlsdesc gd-to-ie relaxation bug

[Cary Coutant]

> gold/ChangeLog:
>
> 2014-11-25  Jing Yu  <jingyu@google.com>
>
>         * aarch64.cc (Relocate::tls_desc_gd_to_ie): Set ldr target
> register to be x0 when to relax TLSDESC_LD64_LO12.

This is OK. Thanks!

-cary