scsi: core: Remove unused extern declarations

These functions have never been implemented since the beginning of git
history.
Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20230809142107.42756-1-yuehaibing@huawei.comReviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_priv.h

@@ -103,7 +103,6 @@ bool scsi_noretry_cmd(struct scsi_cmnd *scmd);
 void scsi_eh_done(struct scsi_cmnd *scmd);
 
 /* scsi_lib.c */
-extern int scsi_maybe_unblock_host(struct scsi_device *sdev);
 extern void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd);
 extern void scsi_queue_insert(struct scsi_cmnd *cmd, int reason);
 extern void scsi_io_completion(struct scsi_cmnd *, unsigned int);
@@ -155,7 +154,6 @@ extern int scsi_sysfs_add_host(struct Scsi_Host *);
 extern int scsi_sysfs_register(void);
 extern void scsi_sysfs_unregister(void);
 extern void scsi_sysfs_device_initialize(struct scsi_device *);
-extern int scsi_sysfs_target_initialize(struct scsi_device *);
 extern struct scsi_transport_template blank_transport_template;
 extern void __scsi_remove_device(struct scsi_device *);