[media] v4l: vsp1: Fix plane stride and size checks

The checks need to be performed on up to two planes, as the third plane,
if present, must have the same stride and size as the second plane.

The code incorrectly performs the checks on at least two planes instead
of at most two planes, fix it.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>