get rid of alloc_pipe_info() argument

not used anymore

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/splice.c b/fs/splice.c
index 9f2a4447..45e645b 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1183,7 +1183,7 @@
 	 */
 	pipe = current->splice_pipe;
 	if (unlikely(!pipe)) {
-		pipe = alloc_pipe_info(NULL);
+		pipe = alloc_pipe_info();
 		if (!pipe)
 			return -ENOMEM;