Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index fa5758c..6888b2c 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -2454,7 +2454,7 @@
 		printk(KERN_INFO "scsi_debug: slave_destroy <%u %u %u %u>\n",
 		       sdp->host->host_no, sdp->channel, sdp->id, sdp->lun);
 	if (devip) {
-		/* make this slot avaliable for re-use */
+		/* make this slot available for re-use */
 		devip->used = 0;
 		sdp->hostdata = NULL;
 	}