[IA64] Compare pointer against NULL, not '0'

When comparing a pointer, it's clearer to compare it to NULL than to 0.

Signed-off-by: Yoann Padioleau <padator@wanadoo.fr>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/arch/ia64/hp/sim/simscsi.c b/arch/ia64/hp/sim/simscsi.c
index bb87682..64248b5 100644
--- a/arch/ia64/hp/sim/simscsi.c
+++ b/arch/ia64/hp/sim/simscsi.c
@@ -101,7 +101,7 @@
 {
 	struct scsi_cmnd *sc;
 
-	while ((sc = queue[rd].sc) != 0) {
+	while ((sc = queue[rd].sc) != NULL) {
 		atomic_dec(&num_reqs);
 		queue[rd].sc = NULL;
 		if (DBG)