Use an empty REG_FRAME_RELATED_EXPR instead.

        * config/ia64/ia64.c (ia64_dwarf_handle_frame_unspec): Remove.
        (TARGET_DWARF_HANDLE_FRAME_UNSPEC): Remove.
        (ia64_expand_epilogue): Emit an empty FRAME_RELATED_EXPR for
        the alloc insn.

From-SVN: r175875