[POWERPC] Export empty_zero_page

Once again, this time with feeling....

						- Ted

>From c91cfaabc17f8a53807a2f31f067a732e34a1550 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@mit.edu>
Date: Wed, 12 Mar 2008 11:50:39 -0400
Subject: Export empty_zero_page

The empty_zero_page symbol is exported by most other architectures
(s390, ia64, x86, um), and an upcoming ext4 patch needs it because
ZERO_PAGE() references empty_zero_page, and we need it to zero out an
unitialized extents in ext4 files.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Paul Mackerras <paulus@samba.org>