[media] media: ov7670: make try_fmt() consistent with 'min_height' and 'min_width'

'min_height' and 'min_width' are variables that allow to specify the minimum
resolution that the sensor will achieve. This patch make v4l2 fmt callbacks
consider this parameters in order to return valid data to user space.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>