scsi: fix integer as NULL pointer warning

drivers/scsi/aha152x.c:3585:60: warning: Using plain integer as NULL pointer
drivers/scsi/aha152x.c:3845:56: warning: Using plain integer as NULL pointer
drivers/scsi/qla1280.c:2814:37: warning: Using plain integer as NULL pointer
drivers/scsi/atp870u.c:750:47: warning: Using plain integer as NULL pointer
drivers/scsi/3w-9xxx.c:1281:36: warning: Using plain integer as NULL pointer
drivers/scsi/3w-9xxx.c:1293:36: warning: Using plain integer as NULL pointer
drivers/scsi/3w-9xxx.c:1301:35: warning: Using plain integer as NULL pointer
drivers/scsi/hptiop.c:447:10: warning: Using plain integer as NULL pointer
drivers/scsi/hptiop.c:457:10: warning: Using plain integer as NULL pointer
drivers/scsi/hptiop.c:479:24: warning: Using plain integer as NULL pointer
drivers/scsi/hptiop.c:483:22: warning: Using plain integer as NULL pointer
drivers/scsi/hptiop.c:1213:23: warning: Using plain integer as NULL pointer
drivers/scsi/hptiop.c:1214:23: warning: Using plain integer as NULL pointer

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/scsi/atp870u.c

@@ -747,7 +747,7 @@ static void send_s870(struct atp_unit *dev,unsigned char c)
 		dev->quhd[c] = 0;
 	}
 	workreq = dev->quereq[c][dev->quhd[c]];
-	if (dev->id[c][scmd_id(workreq)].curr_req == 0) {	
+	if (dev->id[c][scmd_id(workreq)].curr_req == NULL) {
 		dev->id[c][scmd_id(workreq)].curr_req = workreq;
 		dev->last_cmd[c] = scmd_id(workreq);
 		goto cmd_subp;