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/Bananapi_M2_Ultra_defconfig b/configs/Bananapi_M2_Ultra_defconfig
index 8896d2a..a24c600 100644
--- a/configs/Bananapi_M2_Ultra_defconfig
+++ b/configs/Bananapi_M2_Ultra_defconfig
@@ -15,6 +15,8 @@
 CONFIG_SCSI_AHCI=y
 CONFIG_SYS_I2C_LEGACY=y
 CONFIG_SYS_I2C_MVTWSI=y
+CONFIG_SYS_I2C_SLAVE=0x7f
+CONFIG_SYS_I2C_SPEED=400000
 CONFIG_RGMII=y
 CONFIG_SUN8I_EMAC=y
 CONFIG_AXP_DLDO4_VOLT=2500