Remove more legacy make rules

Change-Id: I7ef2e7fa725ba166c29f3daeb00ddb125c9de99c
diff --git a/bootloader.mk b/bootloader.mk
index 6af0d72..7b5b24e 100644
--- a/bootloader.mk
+++ b/bootloader.mk
@@ -17,7 +17,6 @@
 endif
 
 include $(ROOTDIR)/build/preamble.mk
-include $(ROOTDIR)/board/trustzone.mk
 
 bootloader: $(PRODUCT_OUT)/lk.bin $(PRODUCT_OUT)/bl2.img $(PRODUCT_OUT)/fip.bin $(PRODUCT_OUT)/u-boot-env.bin
 lk-bin: $(PRODUCT_OUT)/lk.bin