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/bcm958305k_defconfig b/configs/bcm958305k_defconfig
index 132234c..dfb9f84 100644
--- a/configs/bcm958305k_defconfig
+++ b/configs/bcm958305k_defconfig
@@ -11,6 +11,7 @@
 # CONFIG_AUTOBOOT is not set
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_ASKENV=y
+CONFIG_MX_CYCLIC=y
 # CONFIG_CMD_FLASH is not set
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_MII=y