Set compatibility flag for 4GB zone on IA64

IA64 traditionally had a 4GB DMA32 zone. Set the compatibility flag
to keep old drivers working.

For new drivers it would be better to use ZONE_DMA32 now. 

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

Index: linux/arch/ia64/Kconfig
===================================================================
--- linux.orig/arch/ia64/Kconfig
+++ linux/arch/ia64/Kconfig
@@ -54,6 +54,10 @@ config IA64_UNCACHED_ALLOCATOR
 	bool
 	select GENERIC_ALLOCATOR
 
+config ZONE_DMA_IS_DMA32
+	bool
+	default y
+
 choice
 	prompt "System type"
 	default IA64_GENERIC