dm snapshot: remove unnecessary NULL checks before vfree() calls

The vfree() function performs input parameter validation.
Thus the NULL pointer test around vfree() calls is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index d6e8817..808b841 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -200,16 +200,11 @@
 
 static void free_area(struct pstore *ps)
 {
-	if (ps->area)
-		vfree(ps->area);
+	vfree(ps->area);
 	ps->area = NULL;
-
-	if (ps->zero_area)
-		vfree(ps->zero_area);
+	vfree(ps->zero_area);
 	ps->zero_area = NULL;
-
-	if (ps->header_area)
-		vfree(ps->header_area);
+	vfree(ps->header_area);
 	ps->header_area = NULL;
 }
 
@@ -605,8 +600,7 @@
 	free_area(ps);
 
 	/* Allocated in persistent_read_metadata */
-	if (ps->callbacks)
-		vfree(ps->callbacks);
+	vfree(ps->callbacks);
 
 	kfree(ps);
 }