pipe: fold file_operations instances in one

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/internal.h b/fs/internal.h
index 4be7823..eaa75f7 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -130,3 +130,8 @@
  * read_write.c
  */
 extern ssize_t __kernel_write(struct file *, const char *, size_t, loff_t *);
+
+/*
+ * pipe.c
+ */
+extern const struct file_operations pipefifo_fops;