media: af9013: change lock detection slightly

Whilst rewritten largely, the basic logic remains same with one
exception: do not return immediately on success case. We are going to
add statistics that function and cannot return too early.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>