rockchip: make_fit_atf.py depends on u-boot

u-boot.itb depends on u-boot-nodtb.bin, which in turn depends on u-boot.
u-boot.its from Rockchip make_fit_atf.py (used by {evb,firefly}-rk3399)
wants to read u-boot but is lacking this dependency, so that u-boot.itb
cannot be built in one go. Detect its use and add the missing dependency.

Reported-by: Yousaf Kaukab <yousaf.kaukab@suse.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

Makefile

@@ -1074,7 +1074,10 @@ U_BOOT_ITS = $(subst ",,$(CONFIG_SPL_FIT_SOURCE))
 else
 ifneq ($(CONFIG_SPL_FIT_GENERATOR),"")
 U_BOOT_ITS := u-boot.its
-$(U_BOOT_ITS): FORCE
+ifeq ($(CONFIG_SPL_FIT_GENERATOR),"arch/arm/mach-rockchip/make_fit_atf.py")
+U_BOOT_ITS_DEPS += u-boot
+endif
+$(U_BOOT_ITS): $(U_BOOT_ITS_DEPS) FORCE
 	$(srctree)/$(CONFIG_SPL_FIT_GENERATOR) \
 	$(patsubst %,arch/$(ARCH)/dts/%.dtb,$(subst ",,$(CONFIG_OF_LIST))) > $@
 endif