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/db-88f6820-gp_defconfig b/configs/db-88f6820-gp_defconfig
index 0ab8722..dbad6e4 100644
--- a/configs/db-88f6820-gp_defconfig
+++ b/configs/db-88f6820-gp_defconfig
@@ -48,6 +48,7 @@
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_SPL_OF_TRANSLATE=y
 CONFIG_AHCI_MVEBU=y
+CONFIG_SYS_I2C_MVTWSI=y
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_SDMA=y
 CONFIG_MMC_SDHCI_MV=y