parisc: Add archclean Makefile target

Apparently we don't have an archclean target in our
arch/parisc/Makefile, so files in there never get cleaned out by make
mrproper.  This, in turn means that the sizes.h file in
arch/parisc/boot/compressed never gets removed and worse, when you
transition to an O=build/parisc[64] build model it overrides the
generated file.  The upshot being my bzImage was building with a SZ_end
that was too small.

I fixed it by making mrproper clean everything.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: stable@vger.kernel.org # v4.20+
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/Makefile

@@ -180,5 +180,8 @@ define archhelp
 	@echo  '  zinstall	- Install compressed vmlinuz kernel'
 endef
 
+archclean:
+	$(Q)$(MAKE) $(clean)=$(boot)
+
 archheaders:
 	$(Q)$(MAKE) $(build)=arch/parisc/kernel/syscalls all

arch/parisc/boot/compressed/Makefile

@@ -12,6 +12,7 @@ UBSAN_SANITIZE := n
 targets := vmlinux.lds vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2
 targets += vmlinux.bin.xz vmlinux.bin.lzma vmlinux.bin.lzo vmlinux.bin.lz4
 targets += misc.o piggy.o sizes.h head.o real2.o firmware.o
+targets += real2.S firmware.c
 
 KBUILD_CFLAGS := -D__KERNEL__ -O2 -DBOOTLOADER
 KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING