[media] v4l: use i2c_smbus_read_word_swapped

Function ensures that error codes don't get mangled.
Dependant on:
which is working it's way through the i2c tree.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>