arm/boot: Allow boards to modify the FDT blob

Add a callback hook in arm_boot_info to allow board models to
modify the device tree blob if they need to. (The major expected
use case is to add virtio-mmio nodes for virtio-mmio transports
that exist in QEMU but not in the hardware.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1373977512-28932-7-git-send-email-peter.maydell@linaro.org

hw/arm/boot.c

@@ -294,6 +294,11 @@ static int load_dtb(hwaddr addr, const struct arm_boot_info *binfo)
             goto fail;
         }
     }
+
+    if (binfo->modify_dtb) {
+        binfo->modify_dtb(binfo, fdt);
+    }
+
     qemu_devtree_dumpdtb(fdt, size);
 
     cpu_physical_memory_write(addr, fdt, size);