target/arm: Add FEAT_NV2 to max, neoverse-n2, neoverse-v1 CPUs

Enable FEAT_NV2 on the 'max' CPU, and stop filtering it out for
the Neoverse N2 and Neoverse V1 CPUs.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Miguel Luis <miguel.luis@oracle.com>