media: ti-vpe: cal: fix write to unallocated memory

The asd allocated with v4l2_async_notifier_add_fwnode_subdev() must be
of size cal_v4l2_async_subdev, otherwise access to
cal_v4l2_async_subdev->phy will go to unallocated memory.

Fixes: 8fcb7576 ("media: ti-vpe: cal: Allow multiple contexts per subdev notifier")
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>