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/maxbcm_defconfig b/configs/maxbcm_defconfig
index f4e493c..816d1ac 100644
--- a/configs/maxbcm_defconfig
+++ b/configs/maxbcm_defconfig
@@ -36,6 +36,7 @@
 CONFIG_ENV_SPI_MAX_HZ=50000000
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_SPL_OF_TRANSLATE=y
+CONFIG_SYS_I2C_MVTWSI=y
 # CONFIG_MMC is not set
 CONFIG_SPI_FLASH_MACRONIX=y
 CONFIG_SPI_FLASH_SPANSION=y