boot: Introduce BOOTSTD_MENU to control bootflow menu build

The bootflow_menu.c code depends on e.g. scene_txt_set_font(),
which is only built when CONFIG_EXPO is enabled. Introduce new
Kconfig symbol BOOTSTD_MENU which depends on EXPO to prevent
triggering errors like these in case e.g. CONFIG_VIDEO=n :

"
boot/bootflow_menu.c:158:(.text+0x8851): undefined reference to `scene_txt_set_font'
"

Make the symbol depend on BOOTSTD_FULL as well to get rid of
the Makefile dependency workaround. Since BOOTSTD_FULL is not
available in SPL, do not define SPL variant of BOOTSTD_MENU.

Fix up bootflow test accordingly.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/boot/Makefile b/boot/Makefile
index b24f806..0e0afad 100644
--- a/boot/Makefile
+++ b/boot/Makefile
@@ -24,6 +24,7 @@
 obj-$(CONFIG_$(PHASE_)BOOTSTD) += bootmeth-uclass.o
 obj-$(CONFIG_$(PHASE_)BOOTSTD) += bootstd-uclass.o
 
+obj-$(CONFIG_$(PHASE_)BOOTSTD_MENU) += bootflow_menu.o
 obj-$(CONFIG_$(PHASE_)BOOTSTD_PROG) += prog_boot.o
 
 obj-$(CONFIG_$(PHASE_)BOOTMETH_EXTLINUX) += bootmeth_extlinux.o
@@ -35,10 +36,6 @@
 obj-$(CONFIG_$(PHASE_)BOOTMETH_SCRIPT) += bootmeth_script.o
 obj-$(CONFIG_$(PHASE_)CEDIT) += cedit.o
 obj-$(CONFIG_$(PHASE_)BOOTMETH_EFI_BOOTMGR) += bootmeth_efi_mgr.o
-ifdef CONFIG_$(PHASE_)BOOTSTD_FULL
-obj-$(CONFIG_$(PHASE_)EXPO) += bootflow_menu.o
-obj-$(CONFIG_$(PHASE_)BOOTSTD) += bootflow_menu.o
-endif
 
 obj-$(CONFIG_$(PHASE_)OF_LIBFDT) += fdt_support.o
 obj-$(CONFIG_$(PHASE_)FDT_SIMPLEFB) += fdt_simplefb.o