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/kp_imx53_defconfig b/configs/kp_imx53_defconfig
index 4a2d8af..abca864 100644
--- a/configs/kp_imx53_defconfig
+++ b/configs/kp_imx53_defconfig
@@ -38,6 +38,7 @@
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_I2C_SET_DEFAULT_BUS_NUM=y
 CONFIG_I2C_DEFAULT_BUS_NUMBER=0x1
+CONFIG_SYS_I2C_MXC=y
 CONFIG_FSL_ESDHC_IMX=y
 CONFIG_MTD=y
 CONFIG_PHYLIB=y