ram: stm32mp1: add driver

Add driver and binding for stm32mp1 ddr controller and phy

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/drivers/ram/Makefile b/drivers/ram/Makefile
index 51ae6be..3820d03 100644
--- a/drivers/ram/Makefile
+++ b/drivers/ram/Makefile
@@ -6,6 +6,7 @@
 #
 obj-$(CONFIG_RAM) += ram-uclass.o
 obj-$(CONFIG_SANDBOX) += sandbox_ram.o
+obj-$(CONFIG_STM32MP1_DDR) += stm32mp1/
 obj-$(CONFIG_STM32_SDRAM) += stm32_sdram.o
 obj-$(CONFIG_ARCH_BMIPS) += bmips_ram.o