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_qspi_defconfig b/configs/ls1088ardb_qspi_defconfig
index 7c769a1..27433b6 100644
--- a/configs/ls1088ardb_qspi_defconfig
+++ b/configs/ls1088ardb_qspi_defconfig
@@ -49,6 +49,8 @@
 CONFIG_SCSI_AHCI=y
 CONFIG_SATA_CEVA=y
 CONFIG_SYS_I2C_LEGACY=y
+CONFIG_SYS_MXC_I2C1_SPEED=40000000
+CONFIG_SYS_MXC_I2C2_SPEED=40000000
 CONFIG_SYS_I2C_EEPROM_ADDR=0x57
 CONFIG_FSL_ESDHC=y
 CONFIG_MTD=y