aarch64: Add initial tuning model for cortex-a320 core

gcc/ChangeLog:

	* config/aarch64/aarch64-cores.def (cortex-a320): Update core.
	* config/aarch64/aarch64.cc: Add cortexa320.h.
	* config/aarch64/tuning_models/cortexa320.h: New file.
3 files changed