message: only by using the VGA interface, the header will be included
diff: #include <hermit/spinlock.h>
  #include <asm/atomic.h>
  #include <asm/processor.h>
  +#ifdef CONFIG_VGA
  #include <asm/vga.h>
  +#endif
  #include <asm/uart.h>
  static atomic_int32_t kmsg_counter = ATOMIC_INIT(-1);
  