db845c: Add rb5 support in db845c-userdebug build target

* Enabled multiple appended DTBs support to allow db845c
boot.img/vendor_boot.img to boot on rb5 as well.

* Introduced a vendor.hw property which will be used to run
device specific services.

* Folded Caleb's HDMI audio routing fix.

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Change-Id: I779d01946ae359d5c405d959419e29460083e5df
diff --git a/build/tasks/kernel.mk b/build/tasks/kernel.mk
new file mode 100644
index 0000000..959347b
--- /dev/null
+++ b/build/tasks/kernel.mk
@@ -0,0 +1,8 @@
+ifneq ($(filter db845c, $(TARGET_DEVICE)),)
+
+$(PRODUCT_OUT)/dtb.img: $(DB845C_KERNEL_DIR)/sdm845-db845c.dtb
+	-cat $(DB845C_KERNEL_DIR)/sdm845-db845c.dtb $(DB845C_KERNEL_DIR)/qrb5165-rb5.dtb > $@
+
+droidcore: $(PRODUCT_OUT)/dtb.img
+
+endif