V4L/DVB (5468): Don't mirror ov7670 images by default

Don't mirror ov7670 images by default.

The ov7670 sensor driver sets the mirror bit by default, which is not
the desired mode.  OLPC has been running with this patch for a while.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>