scsi: core: Delete scsi_use_blk_mq

Module param scsi_use_blk_mq has not been referenced for some time, so zap
it.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: John Garry <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/scsi.c

···
 module_param(scsi_logging_level, int, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(scsi_logging_level, "a bit mask of logging levels");
 
-/* This should go away in the future, it doesn't do anything anymore */
-bool scsi_use_blk_mq = true;
-module_param_named(use_blk_mq, scsi_use_blk_mq, bool, S_IWUSR | S_IRUGO);
-
 static int __init init_scsi(void)
 {
 	int error;

drivers/scsi/scsi_priv.h

···
 extern void scsi_exit_hosts(void);
 
 /* scsi.c */
-extern bool scsi_use_blk_mq;
 int scsi_init_sense_cache(struct Scsi_Host *shost);
 void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd);
 #ifdef CONFIG_SCSI_LOGGING