media: qcom: iris: Set file->private_data in iris_v4l2_fh_(de)init()

media: qcom: iris: Set file->private_data in iris_v4l2_fh_(de)init()

In preparation for a tree-wide rework automated with coccinelle that
will affect file->private_data, v4l2_fh_add() and v4l2_fh_del(), move
setting file->private_data from the callers to the iris_v4l2_fh_init()
and iris_v4l2_fh_deinit() functions. There is not functional change yet.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>