mx6: standardise CONFIG_CMD_CACHE

Move CONFIG_CMD_CACHE to mx6_common and standardise the way it's defined.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Tom Rini <trini at konsulko.com>
diff --git a/include/configs/mx6_common.h b/include/configs/mx6_common.h
index c9cd648..233c6d2 100644
--- a/include/configs/mx6_common.h
+++ b/include/configs/mx6_common.h
@@ -89,6 +89,10 @@
 #define CONFIG_SYS_MAXARGS	32
 #define CONFIG_SYS_BARGSIZE	CONFIG_SYS_CBSIZE
 
+#ifndef CONFIG_SYS_DCACHE_OFF
+#define CONFIG_CMD_CACHE
+#endif
+
 /* GPIO */
 #define CONFIG_MXC_GPIO
 #define CONFIG_CMD_GPIO