[media] em28xx-camera: fix return value checks on sensor probing

Since commit e63b009d the returned error code in case of not connected/responding
i2c clients is ENXIO isntead of ENODEV, which causes several error messages on
sensor probing.
Fix the i2c return value checks on sensor probing to silence these warnings.

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>