pipe: drop an always true check in anon_pipe_write()

The check operates on the stale value of 'head' and always loops back.

Just do it unconditionally. No functional changes.

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20250303230409.452687-2-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/pipe.c

@@ -529,10 +529,9 @@ anon_pipe_write(struct kiocb *iocb, struct iov_iter *from)
 
 			if (!iov_iter_count(from))
 				break;
-		}
 
-		if (!pipe_full(head, pipe->tail, pipe->max_usage))
 			continue;
+		}
 
 		/* Wait for buffer space to become available. */
 		if ((filp->f_flags & O_NONBLOCK) ||