M68k VT updates:
  - Include <linux/vt_kern.h> instead of copying the kd_mksound() prototype
  - Lots of stuff depends on CONFIG_VT:
      o SYSRQ_KEY
      o kd_mksound()
      o mach_keyb_init()
      o mach_kbdrate()
      o mach_kbd_leds()
      o mach_kbd_translate()
      o mach_sysrq_xlate()
      o Atari keyboard and joystick drivers
  - There's no need to provide dummy routines for kbd{rate,_leds}()
  - dummy_con depends on CONFIG_DUMMY_CONSOLE