powerpc: Fix incorrect comment about interrupt stack allocation

We now allow interrupt stacks anywhere in the first segment which can be
256M or 1TB. Fix the comment.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index ce6f61c..5a0401f 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -437,8 +437,8 @@
 	unsigned int i;
 
 	/*
-	 * interrupt stacks must be under 256MB, we cannot afford to take
-	 * SLB misses on them.
+	 * Interrupt stacks must be in the first segment since we
+	 * cannot afford to take SLB misses on them.
 	 */
 	for_each_possible_cpu(i) {
 		softirq_ctx[i] = (struct thread_info *)