ANDROID: kbuild: Search external devicetree path when running clean target am: 9f5f2481c9

Original change: https://android-review.googlesource.com/c/kernel/common/+/3095547

Change-Id: I3d31e03ad750c789523e6a436392f62dcea190cc
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
diff --git a/Makefile b/Makefile
index 6de9e72..0ac0eb4 100644
--- a/Makefile
+++ b/Makefile
@@ -1931,7 +1931,9 @@
 
 clean: $(clean-dirs)
 	$(call cmd,rmfiles)
-	@find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
+	@find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) \
+		$(if $(filter-out arch/$(SRCARCH)/boot/dts, $(dtstree)), $(dtstree)) \
+		$(RCS_FIND_IGNORE) \
 		\( -name '*.[aios]' -o -name '*.ko' -o -name '.*.cmd' \
 		-o -name '*.ko.*' \
 		-o -name '*.dtb' -o -name '*.dtb.S' -o -name '*.dt.yaml' \