[media] Raise adapter number limit

The current limit is too low for latest cards with 8+ tuners on a single slot.
IMHO, the most appropriate minimum default is 16.

Signed-off-by: Буди Романто, AreMa Inc <knightrider@are.ma>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>