media: pci: saa7164: Store v4l2_fh pointer in file->private_data

media: pci: saa7164: Store v4l2_fh pointer in file->private_data

Most V4L2 drivers store the v4l2_fh pointer in file->private_data. The
saa7164 instead stores the pointer to the driver-specific structure that
embeds the v4l2_fh. Switch to storing the v4l2_fh pointer itself to
standardize behaviour across drivers. This also prepares for future
refactoring that depends on v4l2_fh being stored in private_data.

This also fixes a bug in the vidioc_g_std() in saa7164-vbi.c that casts
the private_data void pointer to a saa7164_encoder_fh instead of a
saa7164_vbi_fh. The bug has no practical consequence as the two
structures are identical.

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