ANDROID: ARM: Fix dtb list when DTB_IMAGE_NAMES is empty

In the 3.10 kernel, dtb-y is not defined in Makefile.boot anymore
but in dts/Makefile, so it needs to be included too.

Change-Id: I6d6fccf933709bcb6220ce8f12b4b9e2a7c40d63
Signed-off-by: Benoit Goby <benoit@android.com>
diff --git a/arch/arm/boot/Makefile b/arch/arm/boot/Makefile
index 50f8d1b..42f3fdf 100644
--- a/arch/arm/boot/Makefile
+++ b/arch/arm/boot/Makefile
@@ -16,6 +16,7 @@
 ifneq ($(MACHINE),)
 include $(MACHINE)/Makefile.boot
 endif
+include $(srctree)/arch/arm/boot/dts/Makefile
 
 # Note: the following conditions must always be true:
 #   ZRELADDR == virt_to_phys(PAGE_OFFSET + TEXT_OFFSET)