Makefile: Fake external blobs by default with binman

This behaviour is necessary with boards where the binman description
requires processing external blobs, since these may be missing.

Enable it by default, so that CI is happy. Warnings indicate that a valid
image is not produced, as with the --allow-missing option.

Signed-off-by: Simon Glass <sjg@chromium.org>

Makefile

@@ -1320,6 +1320,7 @@ cmd_binman = $(srctree)/tools/binman/binman $(if $(BINMAN_DEBUG),-D) \
                 --toolpath $(objtree)/tools \
 		$(if $(BINMAN_VERBOSE),-v$(BINMAN_VERBOSE)) \
 		build -u -d u-boot.dtb -O . -m --allow-missing \
+		--fake-ext-blobs \
 		-I . -I $(srctree) -I $(srctree)/board/$(BOARDDIR) \
 		-I arch/$(ARCH)/dts -a of-list=$(CONFIG_OF_LIST) \
 		$(foreach f,$(BINMAN_INDIRS),-I $(f)) \
@@ -1331,7 +1332,6 @@ cmd_binman = $(srctree)/tools/binman/binman $(if $(BINMAN_DEBUG),-D) \
 		-a tpl-bss-pad=$(if $(CONFIG_TPL_SEPARATE_BSS),,1) \
 		-a spl-dtb=$(CONFIG_SPL_OF_REAL) \
 		-a tpl-dtb=$(CONFIG_TPL_OF_REAL) \
-		$(if $(BINMAN_FAKE_EXT_BLOBS),--fake-ext-blobs) \
 		$(BINMAN_$(@F))
 
 OBJCOPYFLAGS_u-boot.ldr.hex := -I binary -O ihex