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/km_kirkwood_defconfig b/configs/km_kirkwood_defconfig
index a47593b..4aeb5e7 100644
--- a/configs/km_kirkwood_defconfig
+++ b/configs/km_kirkwood_defconfig
@@ -50,6 +50,7 @@
 CONFIG_SYS_I2C_SOFT=y
 CONFIG_SYS_I2C_SOFT_SLAVE=0x0
 CONFIG_SYS_I2C_MVTWSI=y
+CONFIG_SYS_I2C_SLAVE=0x0
 CONFIG_SYS_I2C_EEPROM_ADDR=0x50
 # CONFIG_MMC is not set
 CONFIG_MTD=y