media: ov2740: Debug log chip ID

Calling the identify function may get delayed till the first stream-on,
add a dev_dbg() to it so that we know when it has run. This is useful
to debug bring-up problems related to regulators / clks / GPIOs.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>