ACPI: APEI: fix synchronous external aborts in user-mode

Before commit 8fcc4ae6 ("arm64: acpi: Make apei_claim_sea()
synchronise with APEI's irq work"), do_sea() would unconditionally
signal the affected task from the arch code. Since that change,
the GHES driver sends the signals.

This exposes a problem as errors the GHES driver doesn't understand
or doesn't handle effectively are silently ignored. It will cause
the errors get taken again, and circulate endlessly. User-space task
get stuck in this loop.

Existing firmware on Kunpeng9xx systems reports cache errors with the
'ARM Processor Error' CPER records.

Do memory failure handling for ARM Processor Error Section just like
for Memory Error Section.

Fixes: 8fcc4ae6

 ("arm64: acpi: Make apei_claim_sea() synchronise with APEI's irq work")
Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Reviewed-by: James Morse <james.morse@arm.com>
[ rjw: Subject edit ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>