scsi: st: Remove redundant variable pointer stp

Variable stp is assigned a value that is never read, the assignment and the
variable stp are redundant and can be removed.

Cleans up clang scan build warning:

drivers/scsi/st.c:4253:7: warning: Although the value stored to 'stp'
is used in the enclosing expression, the value is never actually
read from 'stp' [deadcode.DeadStores]

Link: https://lore.kernel.org/r/20220805115652.2340991-1-colin.i.king@gmail.comSigned-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/st.c

@@ -4246,11 +4246,10 @@ static int st_probe(struct device *dev)
 	struct st_partstat *STps;
 	struct st_buffer *buffer;
 	int i, error;
-	char *stp;
 
 	if (SDp->type != TYPE_TAPE)
 		return -ENODEV;
-	if ((stp = st_incompatible(SDp))) {
+	if (st_incompatible(SDp)) {
 		sdev_printk(KERN_INFO, SDp,
 			    "OnStream tapes are no longer supported;\n");
 		sdev_printk(KERN_INFO, SDp,