ram: starfive: add ddr driver

Add driver for StarFive JH7110 to support ddr initialization in SPL.

Signed-off-by: Yanhong Wang <yanhong.wang@starfivetech.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
diff --git a/drivers/ram/Makefile b/drivers/ram/Makefile
index 83948e2..2b9429c 100644
--- a/drivers/ram/Makefile
+++ b/drivers/ram/Makefile
@@ -20,5 +20,7 @@
 obj-$(CONFIG_IMXRT_SDRAM) += imxrt_sdram.o
 
 obj-$(CONFIG_RAM_SIFIVE) += sifive/
-
+ifdef CONFIG_SPL_BUILD
+obj-$(CONFIG_SPL_STARFIVE_DDR) += starfive/
+endif
 obj-$(CONFIG_ARCH_OCTEON) += octeon/