[AArch64] Add support for the Cortex-A715 CPU

Cortex-A715 is an Armv9-A AArch64 CPU.

This patch introduces support for Cortex-A715.

Technical Reference Manual: https://developer.arm.com/documentation/101590/latest.

Reviewed By: vhscampos

Differential Revision: https://reviews.llvm.org/D136957