ACPI / APEI: Add a notifier chain for unknown (vendor) CPER records

CPER records describing a firmware-first error are identified by GUID.
The ghes driver currently logs, but ignores any unknown CPER records.
This prevents describing errors that can't be represented by a standard
entry, that would otherwise allow a driver to recover from an error.
The UEFI spec calls these 'Non-standard Section Body' (N.2.3 of
version 2.8).

Add a notifier chain for these non-standard/vendor-records. Callers
must identify their type of records by GUID.

Record data is copied to memory from the ghes_estatus_pool to allow
us to keep it until after the notifier has run.

Co-developed-by: James Morse <james.morse@arm.com>
Link: https://lore.kernel.org/r/20200903123456.1823-2-shiju.jose@huawei.com


Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Shiju Jose <shiju.jose@huawei.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>