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/T1024RDB_SPIFLASH_defconfig b/configs/T1024RDB_SPIFLASH_defconfig
index 9f10973..a9424fa 100644
--- a/configs/T1024RDB_SPIFLASH_defconfig
+++ b/configs/T1024RDB_SPIFLASH_defconfig
@@ -36,7 +36,7 @@
 CONFIG_SPL_FSL_PBL=y
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_I2C=y
-CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT=y
+CONFIG_SPL_MPC8XXX_INIT_DDR=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_GREPENV=y