aarch64: Add tuning model for Olympus core.

This patch adds a new tuning model for the NVIDIA Olympus core.
The values used here are based on the Software Optimization Guide
that will be published imminently.

Bootstrapped and tested on aarch64-linux-gnu, no regression.

OK for trunk?
OK to backport to GCC 15?

Signed-off-by: Jennifer Schmitz <jschmitz@nvidia.com>
Co-Authored-By: Dhruv Chawla <dhruvc@nvidia.com>

gcc/ChangeLog:

	* config/aarch64/aarch64-cores.def (olympus): Use olympus tuning
	model.
	* config/aarch64/aarch64.cc: Include olympus.h.
	* config/aarch64/tuning_models/olympus.h: New file.