kernel: Always build dtb targets before dtbo.img

Fixes:
error: unable to open output file
'arch/arm64/boot/dts/google/devices/bluejay/google-base/.gs101-b0.dtb.dts.tmp':
'No such file or directory'

Change-Id: I457062e46062fb3553421d196b432de7d06a49ad
diff --git a/build/tasks/kernel.mk b/build/tasks/kernel.mk
index 337ffef..68775c3 100644
--- a/build/tasks/kernel.mk
+++ b/build/tasks/kernel.mk
@@ -481,8 +481,8 @@
 	@echo "Building dtbo.img"
 	$(hide) find $(DTBO_OUT)/arch/$(KERNEL_ARCH)/boot/dts -type f -name "*.dtbo" | xargs rm -f
 	$(call make-dtbo-target,$(KERNEL_DEFCONFIG))
+	$(call make-dtbo-target,$(TARGET_KERNEL_DTB))
 ifeq ($(BOARD_KERNEL_SEPARATED_DTBO),true)
-	$(call make-dtbo-target,dtbs)
 ifdef BOARD_DTBO_CFG
 	$(MKDTBOIMG) cfg_create $@ $(BOARD_DTBO_CFG) -d $(DTBO_OUT)/arch/$(KERNEL_ARCH)/boot/dts
 else