V4L/DVB (7899): Fixes a few remaining Kbuild issues at common/tuners

- MEDIA_ATTACH now applies also for V4L;

- select a FW_LOADER dependent driver should happen only if HOTPLUG;

- apply the common tuner dependency to all tuners. This helps to avoid latter
  issues.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>