Add register encoding definition for Memory Model Feature Register 2. We need to define it here because we build for ARMv8.0, which doesn't have it. Signed-off-by: Rebecca Cran <rebecca@nuviainc.com> Reviewed-by: Leif Lindholm <leif@nuviainc.com> Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>