ata: libata-scsi: Improve ata_scsi_handle_link_detach()

ata: libata-scsi: Improve ata_scsi_handle_link_detach()

A struct ata_device flags should always be set and cleared with the
device port locked. Testing for a flag should thus also be done while
holding the device port lock. In accordance to this principle, modify
ata_scsi_handle_link_detach() to test and clear the ATA_DFLAG_DETACHED
flag while holding the device port lock.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Niklas Cassel <cassel@kernel.org>