ppc: Rename MPC8XXX_INIT_DDR_SUPPORT to MPC8XXX_INIT_DDR

Rename these options so that CONFIG_IS_ENABLED can be used with them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/ls1021atwr_sdcard_ifc_defconfig b/configs/ls1021atwr_sdcard_ifc_defconfig
index 92fd987..3bf93dd 100644
--- a/configs/ls1021atwr_sdcard_ifc_defconfig
+++ b/configs/ls1021atwr_sdcard_ifc_defconfig
@@ -44,7 +44,7 @@
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR=0xe8
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_I2C=y
-CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT=y
+CONFIG_SPL_MPC8XXX_INIT_DDR=y
 CONFIG_SPL_WATCHDOG=y
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_GREPENV=y