[ARC] Fix to unwinding.

[ARC] Fix to unwinding.

gcc/ChangeLog:
2017-11-03  Cupertino Miranda  <cmiranda@synopsys.com>

        * config/arc/arc.c (arc_save_restore): Corrected CFA note.
        (arc_expand_prologue): Restore blink for millicode.
        * config/arc/linux.h (LINK_EH_SPEC): Defined.

libgcc/ChangeLog:
2017-11-03  Cupertino Miranda  <cmiranda@synopsys.com>
            Vineet Gupta <vgupta@synopsys.com>

        * config.host (arc*-*-linux*): Set md_unwind_header variable.
        * config/arc/linux-unwind-reg.def: New file.
        * config/arc/linux-unwind.h: Likewise.

Co-Authored-By: Vineet Gupta <vgupta@synopsys.com>
From-SVN: r254367