boot/uboot: set DTC path when BR2_TARGET_UBOOT_NEEDS_DTC

In order for host-dtc to get picked up properly we need to set
the DTC path passed to the build explicitly.

See:
https://github.com/u-boot/u-boot/blob/v2023.07.02/Makefile#L420

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

boot/uboot/uboot.mk

@@ -209,6 +209,7 @@ endif
 
 ifeq ($(BR2_TARGET_UBOOT_NEEDS_DTC),y)
 UBOOT_DEPENDENCIES += host-dtc
+UBOOT_MAKE_OPTS += DTC=$(HOST_DIR)/bin/dtc
 endif
 
 ifeq ($(BR2_TARGET_UBOOT_NEEDS_PYTHON3),y)