PCI: PCIe AER: add aer_recover_queue

In addition to native PCIe AER, now APEI (ACPI Platform Error
Interface) GHES (Generic Hardware Error Source) can be used to report
PCIe AER errors too.  To add support to APEI GHES PCIe AER recovery,
aer_recover_queue is added to export the recovery function in native
PCIe AER driver.

Recoverable PCIe AER errors are reported via NMI in APEI GHES.  Then
APEI GHES uses irq_work to delay the error processing into an IRQ
handler.  But PCIe AER recovery can be very time-consuming, so
aer_recover_queue, which can be used in IRQ handler, delays the real
recovery action into the process context, that is, work queue.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>