Convert CONFIG_SPL_COMMON_INIT_DDR to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_COMMON_INIT_DDR

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/P1020RDB-PD_SPIFLASH_defconfig b/configs/P1020RDB-PD_SPIFLASH_defconfig
index 236f07b..e859587 100644
--- a/configs/P1020RDB-PD_SPIFLASH_defconfig
+++ b/configs/P1020RDB-PD_SPIFLASH_defconfig
@@ -74,6 +74,7 @@
 CONFIG_SYS_BR3_PRELIM_BOOL=y
 CONFIG_SYS_BR3_PRELIM=0xFFA00801
 CONFIG_SYS_OR3_PRELIM=0xFFF009F7
+CONFIG_SPL_COMMON_INIT_DDR=y
 CONFIG_DM_I2C=y
 CONFIG_SPL_SYS_I2C_LEGACY=y
 CONFIG_I2C_SET_DEFAULT_BUS_NUM=y