Make i386 compile again with fourth DMA32 zone

The code should deal with an additiona empty zone, so fix up the
#error.

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

Index: linux/arch/i386/kernel/srat.c
===================================================================
--- linux.orig/arch/i386/kernel/srat.c
+++ linux/arch/i386/kernel/srat.c
@@ -137,8 +137,8 @@ static void __init parse_memory_affinity
 		 "enabled and removable" : "enabled" ) );
 }
 
-#if MAX_NR_ZONES != 3
-#error "MAX_NR_ZONES != 3, chunk_to_zone requires review"
+#if MAX_NR_ZONES != 4
+#error "MAX_NR_ZONES != 4, chunk_to_zone requires review"
 #endif
 /* Take a chunk of pages from page frame cstart to cend and count the number
  * of pages in each zone, returned via zones[].