stm32mp1: spl: hang with trace when DDR init failed

When DDR initialization failed, print error message
and stop the SPL execution.
Signed-off-by: NPatrick Delaunay <patrick.delaunay@st.com>

arch/arm/mach-stm32mp/spl.c

@@ -111,7 +111,7 @@ void board_init_f(ulong dummy)
 
 	ret = uclass_get_device(UCLASS_RAM, 0, &dev);
 	if (ret) {
-		debug("DRAM init failed: %d\n", ret);
-		return;
+		printf("DRAM init failed: %d\n", ret);
+		hang();
 	}
 }