media: ov8856: Remove 3280x2464 mode

Remove the 3280x2464 mode as it can't be reproduced and yields
an output resolution of 3264x2448 instead of the desired one.

Furthermore the 3264x2448 resolution is the highest resolution
that the product brief lists.

Since 3280x2464 neither works correctly nor seems to be supported
by the sensor, let's remove it.

Signed-off-by: Robert Foss <robert.foss@linaro.org>