[11] RFR: Fix AArch64 build after merge

[Roman Kennke]

Yes. Thanks,
Roman

> Overlooked a little thing when doing the recent sh/jdk11 merge.
> 
> Trivial fix:
> 
> diff -r 5db068a1c73d src/hotspot/cpu/aarch64/gc/shenandoah/shenandoahBarrierSetAssembler_aarch64.cpp
> --- a/src/hotspot/cpu/aarch64/gc/shenandoah/shenandoahBarrierSetAssembler_aarch64.cpp	Thu Aug 15
> 13:27:31 2019 +0200
> +++ b/src/hotspot/cpu/aarch64/gc/shenandoah/shenandoahBarrierSetAssembler_aarch64.cpp	Thu Aug 15
> 13:28:43 2019 -0400
> @@ -575,7 +575,7 @@
>    __ push_call_clobbered_registers();
> 
>    __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier));
> -  __ blrt(lr, 1, 0, MacroAssembler::ret_type_integral);
> +  __ blr(lr);
>    __ mov(rscratch1, r0);
>    __ pop_call_clobbered_registers();
>    __ mov(r0, rscratch1);
> 
> 
> Testing: aarch64 build, hotspot_gc_shenandoah
>