pipe: fold file_operations instances in one

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/inode.c b/fs/inode.c
index f5f7c06..5b76d9b 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1803,7 +1803,7 @@
 		inode->i_fop = &def_blk_fops;
 		inode->i_rdev = rdev;
 	} else if (S_ISFIFO(mode))
-		inode->i_fop = &def_fifo_fops;
+		inode->i_fop = &pipefifo_fops;
 	else if (S_ISSOCK(mode))
 		inode->i_fop = &bad_sock_fops;
 	else