Drop debug.drv, rework debug rom instead

Makefile

@@ -73,10 +73,6 @@ fate.bs: boot/fat.asm
 %.rom: rom/%.asm utils/fix-rom
 	$(NASM) $(NASM_ARGS) -o $@ $< && utils/fix-rom $@
 
-# rdos drivers
-%.drv:	driver/%.asm
-	$(NASM) $(NASM_ARGS) -o $@ $<
-
 fdimage.img: fat1.bs $(DISTFILES)
 	mformat -C -i $@ -f $(FLOPPY) -B fat1.bs ::
 	mmd -i $@ ::rdos