Implement ACPI APEI ERST feature

Implement ACPI APEI ERST feature

APEI are ACPI4.0 new features. It consists of ERST, BERT, HEST, and
EINJ.  ERST is used to save fault error log to a platform persistent
storage, so that when reboot os can retrieve the error log and handle
it.

This patch is used to implement ERST feature to Xen.  It consists of
3-level hierarchy: operation level, action level, and instru= ction
level.  Instruction do basic io; Action done by sequential
instructions parsed from ACPI ERST table; Operation done by
sequential actions defined by ACPI spec, providing erst_write/
erst_read/ erst_clear interfaces to MCE/ NMI/ PCIe error handling
mechanism, etc.

Signed-off-by: Liu, Jinsong <jinsong.liu@intel.com>