[coreboot] r5511 broke my compile

[Keith Hui]

$  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.