staging: sync: fix return value check in sync_fence_alloc()

In case of error, the function anon_inode_getfile() returns
ERR_PTR() and never returns NULL. The NULL test in the return
value check should be replaced with IS_ERR().
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/sync.c

@@ -261,7 +261,7 @@ static struct sync_fence *sync_fence_alloc(const char *name)
 
 	fence->file = anon_inode_getfile("sync_fence", &sync_fence_fops,
 					 fence, 0);
-	if (fence->file == NULL)
+	if (IS_ERR(fence->file))
 		goto err;
 
 	kref_init(&fence->kref);