V4L/DVB (5626): Marked af9005 driver as experimental and fix dependencies

Marked af9005 driver as experimental and add dependency for qt1010;
Added a dependency on qt1010 in Kconfig;
Corrected the experimental gain  reduction of the mt2060 in case of
strong signal (though it is code included in #ifdef 0).

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