[ARC] Revamp trampoline implementation

[ARC] Revamp trampoline implementation

The new implementation attempts to clean up the existing trampoline
implementation for ARC making it to work for linux type of systems.

gcc/
2018-01-08  Claudiu Zissulescu  <claziss@synopsys.com>

        * config/arc/arc.c (TARGET_TRAMPOLINE_ADJUST_ADDRESS): Delete.
        (emit_store_direct): Likewise.
        (arc_trampoline_adjust_address): Likewise.
        (arc_asm_trampoline_template): New function.
        (arc_initialize_trampoline): Use asm_trampoline_template.
        (TARGET_ASM_TRAMPOLINE_TEMPLATE): Define.
        * config/arc/arc.h (TRAMPOLINE_SIZE): Adjust to 16.
        *config/arc/arc.md (flush_icache): Delete pattern.

From-SVN: r256334