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/A20-Olimex-SOM204-EVB_defconfig b/configs/A20-Olimex-SOM204-EVB_defconfig
index af3eb5b..5b96ddc 100644
--- a/configs/A20-Olimex-SOM204-EVB_defconfig
+++ b/configs/A20-Olimex-SOM204-EVB_defconfig
@@ -16,6 +16,8 @@
 CONFIG_SCSI_AHCI=y
 CONFIG_FASTBOOT_CMD_OEM_FORMAT=y
 CONFIG_SYS_I2C_MVTWSI=y
+CONFIG_SYS_I2C_SLAVE=0x7f
+CONFIG_SYS_I2C_SPEED=400000
 CONFIG_PHY_ADDR=3
 CONFIG_PHY_MICREL=y
 CONFIG_PHY_MICREL_KSZ90X1=y