Makefile: Improve clean a bit

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Makefile

@@ -163,11 +163,13 @@ _clean:
 
 clean: _clean
 	make -f scripts/mw_debug/Makefile clean
+	make -f hello_world/Makefile clean
 
 distclean: _clean
-	rm -f *~ fpga/~
+	rm -f *~ fpga/*~ lib/*~ console/*~ include/*~
 	rm -rf litedram/build
 	rm -f litedram/extras/*~
 	rm -f litedram/gen-src/*~
 	rm -f litedram/gen-src/sdram_init/*~
 	make -f scripts/mw_debug/Makefile distclean
+	make -f hello_world/Makefile distclean

hello_world/Makefile

@@ -29,3 +29,6 @@ hello_world.hex: hello_world.bin
 
 clean:
 	@rm -f *.o hello_world.elf hello_world.bin hello_world.hex
+distclean: clean
+	rm -f *~
+