V4L/DVB (3530): Kconfig: remove VIDEO_AUDIO_DECODER

- removed VIDEO_AUDIO_DECODER Kconfig menu item.
  VIDEO_MSP3400, VIDEO_CS53L32A and VIDEO_WM8775 now
  each have their own menu items.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>