dtbo: Sort the files we found

Change-Id: Iece383362d00d600c5861914b9f2600020229d80
diff --git a/build/tasks/dtbo.mk b/build/tasks/dtbo.mk
index 19e9a7c..02630c8 100644
--- a/build/tasks/dtbo.mk
+++ b/build/tasks/dtbo.mk
@@ -18,7 +18,7 @@
                     break; \
                 fi; \
             done; \
-            $(MKDTIMG) create $@ --page_size=$(BOARD_KERNEL_PAGESIZE) $$(find "$$dtbo_dir" -name '*.dtbo')
+            $(MKDTIMG) create $@ --page_size=$(BOARD_KERNEL_PAGESIZE) $$(find "$$dtbo_dir" -type f -name '*.dtbo' | sort)
     $(hide) chmod a+r $@
 endef