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_plus_defconfig b/configs/Cubietruck_plus_defconfig
index 48d7f34..14e8918 100644
--- a/configs/Cubietruck_plus_defconfig
+++ b/configs/Cubietruck_plus_defconfig
@@ -16,6 +16,7 @@
 CONFIG_AXP_GPIO=y
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
 CONFIG_CONSOLE_MUX=y
+CONFIG_SYS_I2C_MVTWSI=y
 CONFIG_PHY_REALTEK=y
 CONFIG_SUN8I_EMAC=y
 CONFIG_AXP_DLDO3_VOLT=2500