Convert CONFIG_SYS_DDR_RAW_TIMING to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_DDR_RAW_TIMING

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/ls1021aqds_nand_defconfig b/configs/ls1021aqds_nand_defconfig
index cfa81ba..9ab66cd 100644
--- a/configs/ls1021aqds_nand_defconfig
+++ b/configs/ls1021aqds_nand_defconfig
@@ -95,6 +95,7 @@
 CONFIG_SYS_FSL_DDR3=y
 CONFIG_DDR_ECC=y
 CONFIG_ECC_INIT_VIA_DDRCONTROLLER=y
+CONFIG_SYS_DDR_RAW_TIMING=y
 CONFIG_MPC8XXX_GPIO=y
 CONFIG_DM_I2C=y
 CONFIG_SPL_SYS_I2C_LEGACY=y