Makefile: let 'make clean' remove files created by DEVICE_TREE_DEBUG

Originally, 'make DEVICE_TREE_DEBUG=1' only generated extra output on
the console. But since 6cdd7597a2 ("kbuild: Produce diff between base
DT and U-Boot augmented DT if DEVICE_TREE_DEBUG=1"), that has also
left behind lots of files that clutter the repo and are hard to get
rid of manually.

Make sure that a 'make clean' will remove those files, and add them to
.gitignore.

Signed-off-by: Rasmus Villemoes <rv@rasmusvillemoes.dk>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>

.gitignore

@@ -16,6 +16,9 @@
 *.dtb
 *.dtbo
 *.dtb.S
+*.dtb.clean.dts
+*.dtb.diff
+*.dtb.full.dts
 *.elf
 *.exe
 *.fit

Makefile

@@ -2611,6 +2611,7 @@ clean: $(clean-dirs)
 		\( -name '*.[aios]' -o -name '*.ko' -o -name '.*.cmd' \
 		-o -name '*.ko.*' -o -name '*.su' -o -name '*.pyc' \
 		-o -name '*.dtb' -o -name '*.dtbo' -o -name '*.dtb.S' -o -name '*.dt.yaml' \
+		-o -name '*.dtb.clean.dts' -o -name '*.dtb.full.dts' -o -name '*.dtb.diff' \
 		-o -name '*.dwo' -o -name '*.lst' \
 		-o -name '*.su' -o -name '*.mod' -o -name '*.usyms' \
 		-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \