media: atomisp-ov2680: implement enum frame intervals

media: atomisp-ov2680: implement enum frame intervals

Allow the sensor to report the per-resolution frame interval.

It should be noticed that, despite the ov2680 datasheet says
that, for resolutions <= 1280x720, the sensor supports 60fps,
the data at ov2680.h tells otherwise, limiting it to 30fps.

Not sure yet if this is a limitation of atomisp or if it is
just because the tables are incorrect.

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