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/CHIP_defconfig b/configs/CHIP_defconfig
index c245ba9..cd9bdbf 100644
--- a/configs/CHIP_defconfig
+++ b/configs/CHIP_defconfig
@@ -11,6 +11,8 @@
 CONFIG_CMD_DFU=y
 CONFIG_DFU_RAM=y
 CONFIG_SYS_I2C_MVTWSI=y
+CONFIG_SYS_I2C_SLAVE=0x7f
+CONFIG_SYS_I2C_SPEED=400000
 # CONFIG_MMC is not set
 CONFIG_AXP_ALDO3_VOLT=3300
 CONFIG_AXP_ALDO4_VOLT=3300