[PATCH] libata: implement ata_eh_wait()

Implement ata_eh_wait().  On return from this function, it's
guaranteed that the EH which was pending or in progress when the
function was called is complete - including the tailing part of SCSI
EH.  This will be used by hotplug and others to synchronize with EH.

Signed-off-by: Tejun Heo <htejun@gmail.com>

drivers/scsi/libata.h

@@ -103,6 +103,7 @@ extern void ata_schedule_scsi_eh(struct Scsi_Host *shost);
 /* libata-eh.c */
 extern enum scsi_eh_timer_return ata_scsi_timed_out(struct scsi_cmnd *cmd);
 extern void ata_scsi_error(struct Scsi_Host *host);
+extern void ata_port_wait_eh(struct ata_port *ap);
 extern void ata_qc_schedule_eh(struct ata_queued_cmd *qc);
 
 #endif /* __LIBATA_H__ */