ata: libata-core: Synchronize ata_port_detach() with hotplug

The call to async_synchronize_cookie() to synchronize a port removal
and hotplug probe is done in ata_host_detach() right before calling
ata_port_detach(). Move this call at the beginning of ata_port_detach()
to ensure that this operation is always synchronized with probe.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Chia-Lin Kao (AceLan) <acelan.kao@canonical.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>