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/A13-OLinuXino_defconfig b/configs/A13-OLinuXino_defconfig
index a15637f..8c90435 100644
--- a/configs/A13-OLinuXino_defconfig
+++ b/configs/A13-OLinuXino_defconfig
@@ -21,6 +21,8 @@
 CONFIG_DFU_RAM=y
 CONFIG_FASTBOOT_CMD_OEM_FORMAT=y
 CONFIG_SYS_I2C_MVTWSI=y
+CONFIG_SYS_I2C_SLAVE=0x7f
+CONFIG_SYS_I2C_SPEED=400000
 CONFIG_AXP_ALDO3_VOLT=3300
 CONFIG_CONS_INDEX=2
 CONFIG_USB_EHCI_HCD=y