Makefile.target: Update clean command to clean hw/ directory

Now we create object files in a hierarchy under hw/, so the
'clean' target must also be updated to delete those object files.
Rather than using a manual list of subdirectories which will
easily drift out of date, we just delete all .o and .d files
in the target directory hierarchy.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Makefile.target

@@ -193,8 +193,8 @@ qmp-commands-old.h: $(SRC_PATH)/qmp-commands.hx
 	$(call quiet-command,sh $(SRC_PATH)/scripts/hxtool -h < $< > $@,"  GEN   $(TARGET_DIR)$@")
 
 clean:
-	rm -f *.o *.a *~ $(PROGS) nwfpe/*.o fpu/*.o
-	rm -f *.d */*.d tcg/*.o ide/*.o 9pfs/*.o kvm/*.o
+	rm -f *.a *~ $(PROGS)
+	rm -f $(shell find . -name '*.[od]')
 	rm -f hmp-commands.h qmp-commands-old.h gdbstub-xml.c
 ifdef CONFIG_TRACE_SYSTEMTAP
 	rm -f *.stp