nxp: Migrate a number of DDR related symbols to Kconfig

- Guard most of the options in drivers/ddr/fsl/Kconfig with
  SYS_FSL_DDR || SYS_FSL_MMDC.
- Migrate FSL_DMA, DDR_ECC, DDR_ECC_CMD, and ECC_INIT_VIA_DDRCONTROLLER
  to Kconfig.
- Clean up the logic for including the DDR_ECC_CMD code.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/MPC8548CDS_defconfig b/configs/MPC8548CDS_defconfig
index ca6935d..7dcc338 100644
--- a/configs/MPC8548CDS_defconfig
+++ b/configs/MPC8548CDS_defconfig
@@ -25,6 +25,8 @@
 CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_ADDR=0xFFF60000
 CONFIG_DM=y
+CONFIG_DDR_ECC=y
+CONFIG_ECC_INIT_VIA_DDRCONTROLLER=y
 CONFIG_DM_I2C=y
 CONFIG_I2C_SET_DEFAULT_BUS_NUM=y
 CONFIG_SYS_I2C_FSL=y