media: adv748x: Remove g_pixelaspect implementation

media: adv748x: Remove g_pixelaspect implementation

There are no consumer left of g_pixelaspect in the tree, remove the
implementation from the adv748x driver in preparation of removing it
from struct v4l2_subdev_video_ops all together.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://lore.kernel.org/r/20250705083741.77517-3-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>