pxa: add support for D- and I- caches

Tested with OHCI and pxafb drivers - no issues found

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
diff --git a/include/configs/pxa-common.h b/include/configs/pxa-common.h
index 4c1c2c7..7295687 100644
--- a/include/configs/pxa-common.h
+++ b/include/configs/pxa-common.h
@@ -10,6 +10,7 @@
 #define	__CONFIG_PXA_COMMON_H__
 
 #define	CONFIG_DISPLAY_CPUINFO
+#define	CONFIG_SYS_ARM_CACHE_WRITETHROUGH
 
 /*
  * KGDB