[media] gspca - ov519: Fix sensor detection problems

The sensor of some webcams could not be detected due to timing problems
in sensor register reading. This patch adds bridge register readings
before sensor register reading.

Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>