arm: mvebu: db-mv784mp-gp: Enable cache command

Th cache command can be useful sometimes. So lets enable it on the
AXP eval board.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Luka Perkov <luka.perkov@sartura.hr>

include/configs/db-mv784mp-gp.h

@@ -27,6 +27,7 @@
  * Commands configuration
  */
 #define CONFIG_SYS_NO_FLASH		/* Declare no flash (NOR/SPI) */
+#define CONFIG_CMD_CACHE
 #define CONFIG_CMD_DHCP
 #define CONFIG_CMD_ENV
 #define CONFIG_CMD_EXT2