rcar_gen3: drivers: ddr: Move DDR drivers out of staging

Now that DDR drivers are mostly cleaned up , move them out of staging.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Change-Id: I9de63f847a0ef9ac27a79fb0f848c351fd7f4da6
diff --git a/drivers/renesas/rcar/ddr/ddr_b/ddr_b.mk b/drivers/renesas/rcar/ddr/ddr_b/ddr_b.mk
new file mode 100644
index 0000000..2bcc292
--- /dev/null
+++ b/drivers/renesas/rcar/ddr/ddr_b/ddr_b.mk
@@ -0,0 +1,7 @@
+#
+# Copyright (c) 2015-2018, Renesas Electronics Corporation. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+
+BL2_SOURCES += drivers/renesas/rcar/ddr/ddr_b/boot_init_dram.c