target-ppc: Remove address check for logging

One LOG_MMU statement in mmu_helper.c has an odd check on the effective
address being translated.  I can see no reason for this; I suspect it was
a debugging hack from long ago.  This patch removes it.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
