[AArch64] Update NZCV flag-setting instructions' throughput for Neoverse N2 (#174740)
According to the [N2
SWOG](https://developer.arm.com/documentation/109914/latest/),
flag-setting instructions for arithmetic/logical instructions should
have a throughput of 3.
[Similar to the V2
model](https://github.com/llvm/llvm-project/pull/113542).