ata: libata-core: Detach a port devices on shutdown

ata: libata-core: Detach a port devices on shutdown

Modify ata_pci_shutdown_one() to schedule EH to unload a port devices
before freezing and thawing the port. This ensures that drives are
cleanly disabled and transitioned to standby power mode when
a PCI adapter is removed or the system is powered off.

Signed-off-by: Damien Le Moal <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Tested-by: Chia-Lin Kao (AceLan) <[email protected]>
Tested-by: Geert Uytterhoeven <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>