config/arm: add Graviton2

config/arm: add Graviton2

Add meson build configuration for Graviton2 platform
with 64-bit Arm Neoverse N1 cores. This patch makes the
following changes to generic Neoverse N1 config:

1. increase lcore limit to 64
2. increase memory support to 1TB
3. remove +crc from -march as that is default when setting armv8.2

For more information about Graviton2 platform, refer to:
https://aws.amazon.com/ec2/graviton/

Signed-off-by: Vimal Chungath <vcchunga@amazon.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>