imx: Add Makefile dependency for mkimage_fit_atf.sh

The mkimage_fit_atf.sh SPL FIT generator script requires
u-boot-nodtb.bin, but this was not enforced by the Makefile. This could
cause the generator script to be executed before u-boot-nodtb.bin has
been created.

Signed-off-by: Chris Spencer <christopher.spencer@sea.co.uk>
Cc: NXP i.MX U-Boot Team <uboot-imx@nxp.com>
diff --git a/Makefile b/Makefile
index eeb299f..47589e4 100644
--- a/Makefile
+++ b/Makefile
@@ -1133,6 +1133,9 @@
 else
 ifneq ($(CONFIG_SPL_FIT_GENERATOR),"")
 U_BOOT_ITS := u-boot.its
+ifeq ($(CONFIG_SPL_FIT_GENERATOR),"arch/arm/mach-imx/mkimage_fit_atf.sh")
+U_BOOT_ITS_DEPS += u-boot-nodtb.bin
+endif
 ifeq ($(CONFIG_SPL_FIT_GENERATOR),"arch/arm/mach-rockchip/make_fit_atf.py")
 U_BOOT_ITS_DEPS += u-boot
 endif