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/ls1088ardb_sdcard_qspi_SECURE_BOOT_defconfig b/configs/ls1088ardb_sdcard_qspi_SECURE_BOOT_defconfig
index c75f4726..0a21add 100644
--- a/configs/ls1088ardb_sdcard_qspi_SECURE_BOOT_defconfig
+++ b/configs/ls1088ardb_sdcard_qspi_SECURE_BOOT_defconfig
@@ -60,6 +60,8 @@
 CONFIG_SCSI_AHCI=y
 # CONFIG_SPL_BLK is not set
 CONFIG_SYS_I2C_LEGACY=y
+CONFIG_SYS_MXC_I2C1_SPEED=40000000
+CONFIG_SYS_MXC_I2C2_SPEED=40000000
 CONFIG_SYS_I2C_EEPROM_ADDR=0x57
 # CONFIG_SPL_DM_MMC is not set
 CONFIG_FSL_ESDHC=y