AArch64: Add neoversev1_tunings struct

AArch64: Add neoversev1_tunings struct

This patch adds a Neoverse V1-specific tuning struct that currently is
just a deduplication of the N1 struct it was using before and specifying
the SVE width.
This will allow us to tweak Neoverse V1 things in the future as needed.

Bootstrapped and tested on aarch64-none-linux-gnu.

gcc/
	* config/aarch64/aarch64.c (neoversev1_tunings): Define.
	* config/aarch64/aarch64-cores.def (zeus): Use it.
	(neoverse-v1): Likewise.