media: rkisp1: resizer: Fix resizer disable check when starting stream

The resizer is used to scale the image, but also to change the
subsampling of YUV formats. Both the luma and chroma dimensions need to
be taken into account to decide whether or not to enable the resizer.
The current implementation disables the resizer if the chroma vertical
size isn't changed, which would be the case when scaling up by a factor
of 2 vertically while at the same time converting from YUV 4:2:2 to
4:2:0. Fix it by checking the luma sizes too.

While at it, reflow and clarify comments in the function.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>