V4L/DVB (5932): Af9005 fix tuner module unload

This patch removes the useless tuner field and avoids a double free of 
the tuner (either mt2060 or qt1010).

Signed-off-by: Luca Olivetti <luca@ventoso.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>