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/iNet_3W_defconfig b/configs/iNet_3W_defconfig
index 4aeb19b..b04c4db 100644
--- a/configs/iNet_3W_defconfig
+++ b/configs/iNet_3W_defconfig
@@ -15,4 +15,5 @@
 CONFIG_VIDEO_LCD_BL_PWM="PB2"
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
 CONFIG_SPL_I2C=y
+CONFIG_SYS_I2C_MVTWSI=y
 CONFIG_USB_MUSB_HOST=y