$  make
    GEN        build.h
    ROMCC      romstage.inc
    GEN        crt0.S
    CC         mainboard/asus/p2b-ls/crt0.s
    CC         mainboard/asus/p2b-ls/crt0.initobj.o
    LINK       coreboot
    OBJCOPY    coreboot.bootblock
make: *** No rule to make target `src/arch/i386/include/arch/asm.h',
needed by `build/arch/i386/lib/c_start.o'.  Stop.

  

The define ASSEMBLY is now passed by the Makefile for assembler files.

Hence the asm.h construct is no longer needed.

Just drop asm.h includes from your code. If you use the post_code() macro, you can now #include <cpu/x86/post_code.h> instead.