[AArch64] Enable autoprefetcher modelling in the scheduler

[AArch64] Enable autoprefetcher modelling in the scheduler

	* config/aarch64/aarch64-protos.h
	(struct tune_params): Add autoprefetcher_model field.
	* config/aarch64/aarch64.c: Include params.h
	(generic_tunings): Specify autoprefetcher_model value.
	(cortexa53_tunings): Likewise.
	(cortexa57_tunings): Likewise.
	(cortexa72_tunings): Likewise.
	(thunderx_tunings): Likewise.
	(xgene1_tunings): Likewise.
	(aarch64_first_cycle_multipass_dfa_lookahead_guard): New function.
	(TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD_GUARD): Define.
	(aarch64_override_options_internal): Set
	PARAM_SCHED_AUTOPREF_QUEUE_DEPTH param.

From-SVN: r229412