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/A20-Olimex-SOM-EVB_defconfig b/configs/A20-Olimex-SOM-EVB_defconfig
index a3a701e..4bb9815 100644
--- a/configs/A20-Olimex-SOM-EVB_defconfig
+++ b/configs/A20-Olimex-SOM-EVB_defconfig
@@ -15,6 +15,7 @@
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
 CONFIG_SPL_I2C=y
 CONFIG_SCSI_AHCI=y
+CONFIG_SYS_I2C_MVTWSI=y
 CONFIG_PHY_REALTEK=y
 CONFIG_RTL8211X_PHY_FORCE_MASTER=y
 CONFIG_ETH_DESIGNWARE=y