drivers/bios_emulator: Move conditional compilation to Makefile

drivers/bios_emulator/Makefile

drivers/bios_emulator/atibios.c

drivers/bios_emulator/besys.c

drivers/bios_emulator/bios.c

drivers/bios_emulator/biosemu.c

drivers/bios_emulator/x86emu/debug.c

drivers/bios_emulator/x86emu/decode.c

drivers/bios_emulator/x86emu/ops.c

drivers/bios_emulator/x86emu/ops2.c

drivers/bios_emulator/x86emu/prim_ops.c

drivers/bios_emulator/x86emu/sys.c