V4L/DVB (12238): em28xx: call sensor detection code for all webcam entries

With the previous approach, autodetection were working only for the two
generic entries (em275x and em2820 unknown ones). So, if someone would
try to force probing an specific device, the code would not properly run
the autodetection code.

With the new approach, the sensor autodetection will be run not only for
the two generic entries, but also do webcam specific ones.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>