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/Ampe_A76_defconfig b/configs/Ampe_A76_defconfig
index 7cf572d..7bf3dfc 100644
--- a/configs/Ampe_A76_defconfig
+++ b/configs/Ampe_A76_defconfig
@@ -17,5 +17,7 @@
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
 CONFIG_SPL_I2C=y
 CONFIG_SYS_I2C_MVTWSI=y
+CONFIG_SYS_I2C_SLAVE=0x7f
+CONFIG_SYS_I2C_SPEED=400000
 CONFIG_CONS_INDEX=2
 CONFIG_USB_MUSB_HOST=y