Convert CONFIG_SYS_I2C_MXC et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_I2C_MXC
   CONFIG_SYS_I2C_MXC_I2C1
   CONFIG_SYS_I2C_MXC_I2C2
   CONFIG_SYS_I2C_MXC_I2C3
   CONFIG_SYS_I2C_MXC_I2C4

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/colibri_imx6_defconfig b/configs/colibri_imx6_defconfig
index 7a16d3d..3a53faf 100644
--- a/configs/colibri_imx6_defconfig
+++ b/configs/colibri_imx6_defconfig
@@ -11,6 +11,9 @@
 CONFIG_ENV_OFFSET=0xFFFFDE00
 CONFIG_MX6DL=y
 CONFIG_TARGET_COLIBRI_IMX6=y
+CONFIG_SYS_I2C_MXC_I2C1=y
+CONFIG_SYS_I2C_MXC_I2C2=y
+CONFIG_SYS_I2C_MXC_I2C3=y
 CONFIG_DM_GPIO=y
 CONFIG_DEFAULT_DEVICE_TREE="imx6-colibri"
 CONFIG_SPL_TEXT_BASE=0x00908000
@@ -70,6 +73,8 @@
 CONFIG_BOOTCOUNT_ENV=y
 CONFIG_DM_I2C=y
 CONFIG_SPL_SYS_I2C_LEGACY=y
+CONFIG_SYS_I2C_MXC=y
+CONFIG_SYS_MXC_I2C3_SPEED=400000
 CONFIG_SUPPORT_EMMC_BOOT=y
 CONFIG_FSL_USDHC=y
 CONFIG_PHYLIB=y