drivers: ddr: introduce DDR driver for i.MX8M

Introduce DDR driver for i.MX8M. The driver will be used by SPL to
initialze DDR PHY and DDR Controller.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/drivers/ddr/Kconfig b/drivers/ddr/Kconfig
index b764add..d4b393d 100644
--- a/drivers/ddr/Kconfig
+++ b/drivers/ddr/Kconfig
@@ -1 +1,2 @@
 source "drivers/ddr/altera/Kconfig"
+source "drivers/ddr/imx/Kconfig"