The crash reason is that the insn to be moved to stub may be a
relocation spot, so instead of placing the origin insn (that is insn
before-relocation) to the stub, I have to place the relocated one.
Note the relocation involved is non-pc-relative, so it is safe to move
the relocated insn.

gold/ChangeLog:
2015-06-29  Han Shen  <shenhan@google.com>

    * AArch64.cc (Erratum_stub::Insn_utilities): New typedef.
    (Erratum_stub::update_erratum_insn): New method.
    (Stub_table::relocate_stubs): Modified to place relocated insn.
    (AArch64_relobj::fix_errata): Modified gold_assert.

Change-Id: I9d90ac6e569bbbab086f877c7446dc6f9ea96247
(cherry picked from commit 56b06706ebe6bb3decc674b788b6f5b243b8610d)