Makefile: Fix generation of flash.bin u-boot.itb with binman

In case binman is enabled, the u-boot.itb is generated using this tool
and there is no direct u-boot.itb target, but instead the binman tool
must be invoked. Add support for this case.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/Makefile b/Makefile
index 404977e..0486f2e 100644
--- a/Makefile
+++ b/Makefile
@@ -1493,10 +1493,16 @@
 flash.bin: spl/u-boot-spl.bin u-boot.cnt FORCE
 	$(Q)$(MAKE) $(build)=arch/arm/mach-imx $@
 else
+ifeq ($(CONFIG_BINMAN),y)
+flash.bin: spl/u-boot-spl.bin $(INPUTS-y) FORCE
+	$(call if_changed,binman)
+	$(Q)$(MAKE) $(build)=arch/arm/mach-imx $@
+else
 flash.bin: spl/u-boot-spl.bin u-boot.itb FORCE
 	$(Q)$(MAKE) $(build)=arch/arm/mach-imx $@
 endif
 endif
+endif
 
 u-boot.uim: u-boot.bin FORCE
 	$(Q)$(MAKE) $(build)=arch/arm/mach-imx $@