Fix out-of-tree building of "apollon" board.

Signed-off-by: NWolfgang Denk <wd@denx.de>

Makefile

@@ -3257,6 +3257,7 @@ zylonite_config :
 #########################################################################
 
 apollon_config		: unconfig
+	@mkdir -p $(obj)include
 	@echo "#define CONFIG_ONENAND_U_BOOT" > $(obj)include/config.h
 	@$(MKCONFIG) $(@:_config=) arm arm1136 apollon NULL omap24xx
 	@echo "CONFIG_ONENAND_U_BOOT = y" >> $(obj)include/config.mk