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/ls2080ardb_nand_defconfig b/configs/ls2080ardb_nand_defconfig
index 277a484..cd2cab4 100644
--- a/configs/ls2080ardb_nand_defconfig
+++ b/configs/ls2080ardb_nand_defconfig
@@ -27,7 +27,7 @@
 CONFIG_MISC_INIT_R=y
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_I2C=y
-CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT=y
+CONFIG_SPL_MPC8XXX_INIT_DDR=y
 CONFIG_SPL_NAND_SUPPORT=y
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_GREPENV=y