xen-pciback: mark device to be hidden on AER error trigger

xen-pciback: mark device to be hidden on AER error trigger

Some platforms are configured to reboot the machine upon
AER unrecoverable error and some virtualized systems are subject
to security risks described in XSA-124.
This patch allows for simple AER unrecoverable errors containment
together with killing the guest upon receiving of fatal AER error.
Patch stores in xenstore sbdf of passed through device that triggered
AER unrecoverable error. This will allow xend to make device
unassignable until next reboot or special hypervisor hypercall.

OraBug: 24377669

Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Adnan Misherfi <adnan.misherfi@oracle.com>