mediatek/mt8183: Add DRAM resource in ramstage

Add DRAM resource in ramstage to load payload.

BUG=b:80501386
TEST=Load bl31 and depthcharge correctly on Kukui with more patches
     applied.

Change-Id: Ie793b403bbbdb3c231dfa2caef29dcbb596b1a61
Signed-off-by: Tristan Shieh <tristan.shieh@mediatek.com>
Reviewed-on: https://review.coreboot.org/27971
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/mediatek/mt8183/soc.c

@@ -14,7 +14,15 @@
  */
 
 #include <device/device.h>
+#include <soc/emi.h>
 #include <soc/mmu_operations.h>
+#include <symbols.h>
+
+
+static void soc_read_resources(struct device *dev)
+{
+	ram_resource(dev, 0, (uintptr_t)_dram / KiB, sdram_size() / KiB);
+}
 
 static void soc_init(struct device *dev)
 {
@@ -22,6 +30,7 @@ static void soc_init(struct device *dev)
 }
 
 static struct device_operations soc_ops = {
+	.read_resources = soc_read_resources,
 	.init = soc_init,
 };