Convert CONFIG_SYS_I2C_SPEED et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_I2C_SPEED
   CONFIG_SYS_I2C_SLAVE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/Colombus_defconfig b/configs/Colombus_defconfig
index f479d75..31541f8 100644
--- a/configs/Colombus_defconfig
+++ b/configs/Colombus_defconfig
@@ -23,6 +23,8 @@
 CONFIG_SYS_I2C_SOFT_SPEED=50000
 CONFIG_SYS_I2C_SOFT_SLAVE=0x00
 CONFIG_SYS_I2C_MVTWSI=y
+CONFIG_SYS_I2C_SLAVE=0x7f
+CONFIG_SYS_I2C_SPEED=400000
 CONFIG_PHY_REALTEK=y
 CONFIG_ETH_DESIGNWARE=y
 CONFIG_RGMII=y