ACPI: APEI: handle PCIe AER errors in separate function

Move PCIe AER error handling code into a separate function.

Signed-off-by: Tyler Baicar <tbaicar@codeaurora.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>