ACPI, APEI, HEST table parsing

HEST describes error sources in detail; communicating operational
parameters (i.e. severity levels, masking bits, and threshold values)
to OS as necessary. It also allows the platform to report error
sources for which OS would typically not implement support (for
example, chipset-specific error registers).

HEST information may be needed by other subsystems. For example, HEST
PCIE AER error source information describes whether a PCIE root port
works in "firmware first" mode, this is needed by general PCIE AER
error subsystem. So a public HEST tabling parsing interface is
provided.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>