armv8: fsl-layerscape: Move DDR config options to Kconfig

Move DDR3, DDR4 and realted options to Kconfig and clean up existing
uses.

Signed-off-by: York Sun <york.sun@nxp.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/ls1043aqds_qspi_defconfig b/configs/ls1043aqds_qspi_defconfig
index 54e57bb..94c602c 100644
--- a/configs/ls1043aqds_qspi_defconfig
+++ b/configs/ls1043aqds_qspi_defconfig
@@ -4,7 +4,8 @@
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
-CONFIG_SYS_EXTRA_OPTIONS="SYS_FSL_DDR4,QSPI_BOOT"
+CONFIG_SYS_EXTRA_OPTIONS="QSPI_BOOT"
+CONFIG_SYS_FSL_DDR4=y
 CONFIG_QSPI_BOOT=y
 CONFIG_BOOTDELAY=10
 CONFIG_HUSH_PARSER=y