Convert CONFIG_SYS_I2C_MVTWSI to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_I2C_MVTWSI

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/Cubietruck_defconfig b/configs/Cubietruck_defconfig
index 8ec2449..cf77b0e 100644
--- a/configs/Cubietruck_defconfig
+++ b/configs/Cubietruck_defconfig
@@ -19,6 +19,7 @@
 CONFIG_SCSI_AHCI=y
 CONFIG_DFU_RAM=y
 CONFIG_FASTBOOT_CMD_OEM_FORMAT=y
+CONFIG_SYS_I2C_MVTWSI=y
 CONFIG_PHY_REALTEK=y
 CONFIG_ETH_DESIGNWARE=y
 CONFIG_RGMII=y