powerpc/8xx: Fix comment about DIRTY update

Since commit 2321f33790a6c5b80322d907a92d5739e7521a13, dirty handling is not
handled here anymore. So we fix the comment.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <scottwood@freescale.com>
1 file changed