get rid of pipe->inode

it's used only as a flag to distinguish normal pipes/FIFOs from the
internal per-task one used by file-to-file splice.  And pipe->files
would work just as well for that purpose...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/fuse/dev.c

@@ -1319,7 +1319,7 @@ static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
 		page_nr++;
 		ret += buf->len;
 
-		if (pipe->inode)
+		if (pipe->files)
 			do_wakeup = 1;
 	}