[PATCH] powerpc: Fix use of LOADBASE in merge tree

The merge-tree version of LOADBASE actually loads the whole given
address from the toc for ppc64.  The matching OFF macro adjust for
this, using an offset of 0 for ppc64, but we weren't using that in
power4_idle.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>