[AArch64] Fix to Neoverse V2 scheduling model (#88130)

The size of ROB was incorrecty copied from the Neoverse N2, while it has
actually higher value as descibed in

https://community.arm.com/arm-community-blogs/b/infrastructure-solutions-blog/posts/arm-neoverse-v2-platform-best-in-class-cloud-and-ai-ml-performance