FP4: Move DTC_EXT definition to vendor/lineage

Change-Id: I452ec4dabfd6abf052f020fe48527403df873f5f
diff --git a/BoardConfig.mk b/BoardConfig.mk
index bd6012b..add8e0a 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -91,7 +91,6 @@
 BOARD_FLASH_BLOCK_SIZE := 262144 # (BOARD_KERNEL_PAGESIZE * 64)
 BOARD_MKBOOTIMG_ARGS += --header_version $(BOARD_BOOTIMG_HEADER_VERSION)
 BOARD_KERNEL_IMAGE_NAME := Image
-TARGET_KERNEL_ADDITIONAL_FLAGS := DTC_EXT=$(shell pwd)/prebuilts/misc/linux-x86/dtc/dtc
 TARGET_KERNEL_SOURCE := kernel/fairphone/sm7225
 TARGET_KERNEL_CONFIG := FP4_defconfig