Convert CONFIG_MX_CYCLIC to Kconfig

This converts the following to Kconfig:
   CONFIG_MX_CYCLIC

Signed-off-by: Adam Ford <aford173@gmail.com>
Acked-by: David Lechner <david@lechnology.com>
diff --git a/configs/x600_defconfig b/configs/x600_defconfig
index 203e91f..700f620 100644
--- a/configs/x600_defconfig
+++ b/configs/x600_defconfig
@@ -24,6 +24,7 @@
 CONFIG_AUTOBOOT_STOP_STR=" "
 CONFIG_CMD_IMLS=y
 CONFIG_LOOPW=y
+CONFIG_MX_CYCLIC=y
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_NAND=y