Minor GFP_DMA32 comment fix

Pretty obvious

Signed-off-by: Andi Kleen <ak@suse.de>

Index: linux/include/linux/mmzone.h
===================================================================
--- linux.orig/include/linux/mmzone.h
+++ linux/include/linux/mmzone.h
@@ -99,7 +99,7 @@ struct per_cpu_pageset {
 
 /*
  * On machines where it is needed (eg PCs) we divide physical memory
- * into multiple physical zones. On a PC we have 4 zones:
+ * into multiple physical zones. On a 32bit PC we have 4 zones:
  *
  * ZONE_DMA	  < 16 MB	ISA DMA capable memory
  * ZONE_DMA32	     0 MB 	Empty