removed unnecessary includes in RIOTBASE/Makefile

Makefile

@@ -2,9 +2,6 @@ DIRS = $(RIOTCPU)/$(CPU) core drivers sys
 
 .PHONY: all clean doc
 
-include $(RIOTCPU)/$(CPU)/Makefile.include
-include $(RIOTBOARD)/$(BOARD)/Makefile.include
-
 all:
 	mkdir -p $(BINDIR)
 	@for i in $(DIRS) ; do "$(MAKE)" -C $$i ; done ;