Use reserved memory to hold the buffer for the RAM disk to follow the ACPI spec requirement. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com> Reviewed-by: Siyuan Fu <siyuan.fu@intel.com> Reviewed-by: Samer El-Haj-Mahmoud <elhaj@hpe.com>