media: atomisp-ov2722: use v4l2_find_nearest_size()

Instead of reinventing the wheel, use v4l2_find_nearest_size()
in order to get the closest resolution.

This should address a bug where the wrong resolution was
selected.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>