pxa: Disable dcache on palmld, palmtc, zipitz2

These platforms don't include dcache support. Define CONFIG_SYS_DCACHE_OFF
so that functions don't try to call non-existent routines like
flush_dcache_range().

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/include/configs/zipitz2.h b/include/configs/zipitz2.h
index bf6394a..b92f70b 100644
--- a/include/configs/zipitz2.h
+++ b/include/configs/zipitz2.h
@@ -41,6 +41,9 @@
 #define CONFIG_ENV_ADDR			0x40000
 #define CONFIG_ENV_SIZE			0x20000
 
+/* we will never enable dcache, because we have to setup MMU first */
+#define CONFIG_SYS_DCACHE_OFF
+
 #define	CONFIG_SYS_MALLOC_LEN		(128*1024)
 #define	CONFIG_ARCH_CPU_INIT