'make clean' did not descend into arch/$ARCH/dts for arc, m68k, nios2,
sh, xtensa.
Fix it by adding the missing archs to the explicit clean-dirs list.
Signed-off-by: Tobias Deiminger <tdmg@linutronix.de>
clean-files := dt.dtb.S
# Let clean descend into dts directories
-subdir- += ../arch/arm/dts ../arch/microblaze/dts ../arch/mips/dts ../arch/sandbox/dts ../arch/x86/dts ../arch/powerpc/dts ../arch/riscv/dts
+subdir- += ../arch/arc/dts ../arch/arm/dts ../arch/m68k/dts ../arch/microblaze/dts \
+ ../arch/mips/dts ../arch/nios2/dts ../arch/powerpc/dts ../arch/riscv/dts \
+ ../arch/sandbox/dts ../arch/sh/dts ../arch/x86/dts ../arch/xtensa/dts